Algebraic Word Problems and Modeling

62 soru

Soru 41Soru

A logistics company uses two delivery vehicles, Vehicle P and Vehicle Q, to transport cargo between two warehouses that are 240240 miles apart. Vehicle P travels at a constant average speed of rr miles per hour (r>0r > 0). Vehicle Q travels at a constant average speed that is 2020 miles per hour faster than that of Vehicle P. In addition to driving time, Vehicle P requires a flat setup time of 11 hour before departure, while Vehicle Q requires a flat setup time of 22 hours before departure.

Let TP(r)T_P(r) and TQ(r)T_Q(r) represent the total elapsed time in hours (including setup time) required for Vehicle P and Vehicle Q to complete the trip, respectively.

Which of the following statements are true? Select all such statements.

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Cevap: The total elapsed time for Vehicle P, in hours, as a function of its speed rr, is given by TP(r)=240+rrT_P(r) = \frac{240 + r}{r}.; Vehicle P and Vehicle Q take the exact same total elapsed time to complete the trip when r=60r = 60 miles per hour.

Cevap

The correct statements are the algebraic expression for Vehicle P's total time as a function of speed and the equal total elapsed time condition at a speed of 60 miles per hour.
The expression for Vehicle P's total time accurately combines 11 hour of setup time with 240r\frac{240}{r} driving hours to get 240+rr\frac{240+r}{r}. Setting TP(r)=TQ(r)T_P(r) = T_Q(r) yields the quadratic equation r2+20r4800=0r^2 + 20r - 4800 = 0, which correctly solves to r=60r = 60 mph, at which point both vehicles require exactly 55 hours total.

Adım Adım Çözüm

1
Model total elapsed time functions TP(r)T_P(r) and TQ(r)T_Q(r) using setup time plus travel time.
TP(r)=1+240r=240+rrT_P(r) = 1 + \frac{240}{r} = \frac{240 + r}{r} and TQ(r)=2+240r+20T_Q(r) = 2 + \frac{240}{r + 20}.
Total elapsed time is the sum of fixed pre-departure setup overhead and variable driving time.
2
Determine the speed rr where total elapsed times are equal by setting TP(r)=TQ(r)T_P(r) = T_Q(r).
1+240r=2+240r+20    240r240r+20=1    24020=r(r+20)    r2+20r4800=01 + \frac{240}{r} = 2 + \frac{240}{r + 20} \implies \frac{240}{r} - \frac{240}{r + 20} = 1 \implies 240 \cdot 20 = r(r + 20) \implies r^2 + 20r - 4800 = 0. Factoring gives (r60)(r+80)=0(r - 60)(r + 80) = 0, so r=60r = 60 mph.
Solving the rational equation identifies the exact breakeven speed where higher travel efficiency balances extra setup time.
3
Evaluate the remaining candidate assertions against the derived model.
For r>60r > 60, TQ(r)>TP(r)T_Q(r) > T_P(r), invalidating the claim that Vehicle Q is always faster. At r=40r = 40, TP(40)=7T_P(40) = 7 hours and TP(80)=4T_P(80) = 4 hours, giving a decrease of 3742.86%\frac{3}{7} \approx 42.86\%, invalidating the 50%50\% reduction claim.
Fixed setup costs distort simple constant-proportion and percentage changes in total time.

Anahtar Kavram

Algebraic Modeling of Combined Time with Fixed Overhead and Variable Rates
Soru 42Soru

A water purification facility uses a primary filtration system and a secondary filtration system to process untreated water. The primary system operates at a constant rate that is 25%25\% faster than the secondary system. Working together at their normal constant rates, both systems can process a full reservoir of 36,00036,000 gallons in 88 hours.

On a day when the primary system operates at only 80%80\% of its normal rate due to maintenance while the secondary system operates at its normal rate, both systems work together for 66 hours. At that point, the primary system is shut down completely. How many additional hours will it take the secondary system, working alone at its normal rate, to process the remainder of the reservoir?

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Cevap: 6.06.0 hours

Cevap

6.06.0 hours
The correct answer of 6.06.0 hours is derived by establishing that the combined normal processing rate is 4,5004,500 gal/hr. Since the primary system is 25%25\% faster than the secondary system (P=1.25SP = 1.25S), the secondary rate is 2,0002,000 gal/hr and the primary rate is 2,5002,500 gal/hr. At 80%80\% efficiency, the primary system operates at 2,0002,000 gal/hr, making the joint rate 4,0004,000 gal/hr. In 66 hours, 24,00024,000 gallons are processed, leaving 12,00012,000 gallons. The secondary system working alone at 2,0002,000 gal/hr processes the remaining volume in exactly 6.06.0 hours.

Adım Adım Çözüm

1
Determine the combined normal operating rate and set up individual rates.
Combined rate = 4,5004,500 gal/hr; Secondary rate = 2,0002,000 gal/hr; Primary rate = 2,5002,500 gal/hr.
The combined rate is 36,000 gallons8 hours=4,500 gal/hr\frac{36,000\text{ gallons}}{8\text{ hours}} = 4,500\text{ gal/hr}. Let SS be the secondary rate. The primary rate is 1.25S1.25S. Thus, S+1.25S=2.25S=4,500S + 1.25S = 2.25S = 4,500, yielding S=2,000 gal/hrS = 2,000\text{ gal/hr} and P=2,500 gal/hrP = 2,500\text{ gal/hr}.
2
Calculate the reduced primary rate and the total water processed in the first 6 hours.
24,00024,000 gallons processed in the first 6 hours.
During maintenance, the primary system operates at 80%80\% of 2,500 gal/hr2,500\text{ gal/hr}, which is 0.80×2,500=2,000 gal/hr0.80 \times 2,500 = 2,000\text{ gal/hr}. The combined rate during this period is 2,000+2,000=4,000 gal/hr2,000 + 2,000 = 4,000\text{ gal/hr}. Over 6 hours, the volume processed is 4,000×6=24,000 gallons4,000 \times 6 = 24,000\text{ gallons}.
3
Find the remaining volume of water to process.
12,00012,000 gallons remaining.
Subtract the volume processed from the total reservoir capacity: 36,00024,000=12,000 gallons36,000 - 24,000 = 12,000\text{ gallons}.
4
Calculate the time required for the secondary system alone to process the remainder.
6.06.0 hours.
Divide the remaining volume by the normal secondary system rate S=2,000 gal/hrS = 2,000\text{ gal/hr}: 12,000 gallons2,000 gal/hr=6.0 hours\frac{12,000\text{ gallons}}{2,000\text{ gal/hr}} = 6.0\text{ hours}.

Anahtar Kavram

Linear rate modeling and percentage rate adjustment in combined work problems
Tahmini Süre:2m 30s
Soru 43Soru

A theater sold a total of 500500 tickets for an evening performance, consisting of VIP tickets priced at $80\$80 each and General Admission tickets priced at $50\$50 each. On the day of the show, a promotional discount of 20%20\% was applied to all General Admission tickets, while VIP ticket prices remained unchanged. If the total revenue collected from ticket sales was $31,000\$31,000, which of the following statements must be true? Select all such statements.

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Cevap: More than 70% of the total revenue was generated from VIP ticket sales.; The number of VIP tickets sold was 50 greater than the number of General Admission tickets sold.

Cevap

The statements confirming that more than 70% of total revenue came from VIP ticket sales and that 50 more VIP tickets were sold than General Admission tickets are correct.
The system of equations V+G=500V + G = 500 and 80V+40G=31,00080V + 40G = 31,000 yields V=275V = 275 VIP tickets and G=225G = 225 General Admission tickets. The VIP revenue is 22,000,whichisapproximately70.9722,000, which is approximately 70.97% of the total 31,000 revenue (greater than 70%). Additionally, the difference 275225=50275 - 225 = 50 confirms that 50 more VIP tickets were sold than General Admission tickets.

Adım Adım Çözüm

1
Define variables and determine the discounted price of General Admission tickets.
Let VV be the number of VIP tickets and GG be the number of General Admission tickets. The discounted price for General Admission tickets is $50×(10.20)=$40\$50 \times (1 - 0.20) = \$40.
Establishing correct variable representations and effective unit prices is required to build the revenue model.
2
Set up and solve the system of linear equations.
V+G=500V + G = 500 and 80V+40G=31,00080V + 40G = 31,000. Substituting G=500VG = 500 - V gives 80V+40(500V)=31,000    40V=11,000    V=27580V + 40(500 - V) = 31,000 \implies 40V = 11,000 \implies V = 275. Thus, G=225G = 225.
Solving the linear system determines the exact quantity of each ticket type sold.
3
Calculate revenue shares and verify each statement.
VIP revenue = 275×$80=$22,000275 \times \$80 = \$22,000. Revenue share of VIP = 22,00031,00070.97%>70%\frac{22,000}{31,000} \approx 70.97\% > 70\%. Ticket difference = 275225=50275 - 225 = 50. Ratio V:G=275:225=11:9V:G = 275:225 = 11:9.
Evaluating each calculated metric against the given statements determines which statements must be true.

Anahtar Kavram

Linear word problems involving systems of equations and percentage modifications.
Tahmini Süre:2m 0s
Soru 44Soru

A manufacturing plant operates two automated production lines, Assembly Line X and Assembly Line Y. Assembly Line Y operates at a standard rate that is 25%25\% faster than the standard rate of Assembly Line X. During a specific shift, Assembly Line X operated for 44 hours at its standard rate, after which its processing rate decreased by 20%20\% for an additional 22 hours due to maintenance. Assembly Line Y began operating 11 hour after Line X started; it operated at its standard rate for 44 hours, and then operated for another 22 hours at 80%80\% of its standard rate. If the two lines produced a combined total of 2,7722,772 units during this shift, what was the standard operating rate of Assembly Line X, in units per hour?

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Cevap: 220

Cevap

The standard operating rate of Assembly Line X is 220 units per hour.
Assembly Line X produces 4r4r units in its first 4 hours and 1.6r1.6r units in its final 2 hours, totaling 5.6r5.6r units. Assembly Line Y produces 4×1.25r=5r4 \times 1.25r = 5r units in its first 4 hours and 2×(0.80×1.25r)=2r2 \times (0.80 \times 1.25r) = 2r units in its final 2 hours, totaling 7r7r units. The sum of their outputs is 5.6r+7r=12.6r=2,7725.6r + 7r = 12.6r = 2,772. Dividing 2,7722,772 by 12.612.6 gives r=220r = 220.

Adım Adım Çözüm

1
Set up rate expressions for both assembly lines using a single variable
Standard rate of Line X = rr; Standard rate of Line Y = 1.25r1.25r
Line Y is 25% faster than Line X, so its rate is r+0.25r=1.25rr + 0.25r = 1.25r.
2
Calculate the total work done by Assembly Line X
Line X output = 4(r)+2(0.80r)=5.6r4(r) + 2(0.80r) = 5.6r units
Line X worked 4 hours at 100% rate and 2 hours at 80% rate.
3
Calculate the total work done by Assembly Line Y
Line Y output = 4(1.25r)+2(0.80×1.25r)=5r+2r=7r4(1.25r) + 2(0.80 \times 1.25r) = 5r + 2r = 7r units
Line Y worked 4 hours at full rate 1.25r1.25r and 2 hours at 80% of 1.25r1.25r, which equals rate rr.
4
Equate combined production to 2,772 units and solve for rr
5.6r+7r=12.6r=2,772    r=2205.6r + 7r = 12.6r = 2,772 \implies r = 220
Dividing the total combined output by the total rate multiplier 12.6 yields the baseline standard rate.

Anahtar Kavram

Algebraic Modeling of Staggered Work and Variable Production Rates
Tahmini Süre:2m 30s
Soru 45Soru

An agricultural facility uses two automated irrigation systems, System P and System Q, to water a field. System P pumps water at a constant rate of 120120 gallons per hour after requiring an initial setup overhead of 3030 minutes (0.50.5 hours). System Q pumps water at a constant rate of 180180 gallons per hour after requiring an initial setup overhead of 4545 minutes (0.750.75 hours). Both systems begin their setup process at the exact same time and operate continuously until a combined total of 1,6051,605 gallons of water has been pumped. Which of the following statements must be true? Select all such statements.

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Cevap: The total elapsed time from when setup began until the target volume was reached is 66 hours.; System Q pumped 285285 more gallons of water than System P.; The ratio of the volume of water pumped by System P to that pumped by System Q is 44:6344:63.

Cevap

The correct statements are: the total elapsed time from when setup began is 6 hours, System Q pumped 285 more gallons than System P, and the ratio of water pumped by System P to System Q is 44:63.
Solving the combined linear rate model yields a total elapsed time of 6 hours. With this duration, System P operates for 5.5 hours producing 660 gallons, and System Q operates for 5.25 hours producing 945 gallons. This confirms that the total time is 6 hours, System Q produces 285 more gallons than System P (945 - 660 = 285), and the ratio of System P's volume to System Q's volume is 660:945, which simplifies to 44:63.

Adım Adım Çözüm

1
Define the variable for total time and establish time expressions for active pumping.
Let tt be the total elapsed time in hours since both systems began setup (t0.75t \geq 0.75). System P actively pumps for (t0.5)(t - 0.5) hours, and System Q actively pumps for (t0.75)(t - 0.75) hours.
Setup overhead delays the start of pumping, so active pumping duration equals total elapsed time minus setup time.
2
Set up and solve the linear rate equation for combined total volume.
120(t0.5)+180(t0.75)=1605    120t60+180t135=1605    300t195=1605    300t=1800    t=6120(t - 0.5) + 180(t - 0.75) = 1605 \implies 120t - 60 + 180t - 135 = 1605 \implies 300t - 195 = 1605 \implies 300t = 1800 \implies t = 6 hours.
The sum of the volumes produced by both systems must equal the target total of 1,605 gallons.
3
Calculate individual pumping times and volumes produced by each system.
System P: active time =5.5= 5.5 hours, volume =120×5.5=660= 120 \times 5.5 = 660 gallons. System Q: active time =5.25= 5.25 hours, volume =180×5.25=945= 180 \times 5.25 = 945 gallons.
Individual volumes are required to evaluate statements regarding volume differences, percentages, and ratios.
4
Evaluate each given statement against the calculated values.
Elapsed time is 66 hours (True). Volume difference is 945660=285945 - 660 = 285 gallons (True). Active pumping time for P is 5.55.5 hours, not 5.255.25 hours (False). Percentage for Q is 945/160558.88%<60%945 / 1605 \approx 58.88\% < 60\% (False). Ratio P to Q is 660:945=44:63660 : 945 = 44 : 63 (True).
Determines which of the statements must be selected.

Anahtar Kavram

Linear Modeling with Combined Work Rates and Staggered Start Times
Soru 46Soru

A laboratory processes two types of chemical samples, Type A and Type B. Processing each Type A sample requires 4040 minutes and costs $30\$30, while processing each Type B sample requires 3030 minutes and costs $50\$50. On a given day, the laboratory spent a total of 2020 hours processing these two types of samples at a total cost of $1,450\$1,450. How many more Type B samples were processed than Type A samples?

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Cevap: 5

Cevap

5 more Type B samples were processed than Type A samples.
The correct answer is 5. By defining xx as the number of Type A samples and yy as the number of Type B samples, we construct the time equation 40x+30y=1,20040x + 30y = 1,200 and cost equation 30x+50y=1,45030x + 50y = 1,450. Solving this system yields x=15x = 15 and y=20y = 20. The difference yx=2015=5y - x = 20 - 15 = 5.

Adım Adım Çözüm

1
Define variables and convert units to maintain consistency.
Let xx be the number of Type A samples and yy be the number of Type B samples. Total time available is 20 hours×60 minutes/hour=1,200 minutes20 \text{ hours} \times 60 \text{ minutes/hour} = 1,200 \text{ minutes}.
Time specifications for individual samples are given in minutes, so total time must also be in minutes.
2
Set up a system of two linear equations representing total time and total cost.
Time equation: 40x+30y=1,200    4x+3y=12040x + 30y = 1,200 \implies 4x + 3y = 120. Cost equation: 30x+50y=1,450    3x+5y=14530x + 50y = 1,450 \implies 3x + 5y = 145.
The total processing time is the sum of time spent on each sample type, and total cost is the sum of costs for each sample type.
3
Solve the system of equations using elimination.
Multiply the time equation by 3: 12x+9y=36012x + 9y = 360. Multiply the cost equation by 4: 12x+20y=58012x + 20y = 580. Subtracting the first from the second gives 11y=220    y=2011y = 220 \implies y = 20. Substitute y=20y = 20 into 4x+3(20)=120    4x=60    x=154x + 3(20) = 120 \implies 4x = 60 \implies x = 15.
Eliminating xx allows direct calculation of yy, which then yields xx.
4
Calculate the difference requested by the problem.
Difference = yx=2015=5y - x = 20 - 15 = 5.
The question specifically asks for how many more Type B samples were processed than Type A samples.

Anahtar Kavram

Formulating and solving systems of linear equations from real-world rate and budget constraints.
Tahmini Süre:1m 45s
Soru 47Soru

A commercial bakery uses two automated ovens, Oven X and Oven Y, to bake identical orders of bread. Working alone at its constant rate, Oven X bakes a full order of bread in 88 hours, while Oven Y, working alone at its constant rate, bakes the same order in 1212 hours. Both ovens begin baking a full order together at 8:00 a.m. At 10:00 a.m., Oven X shuts down due to a maintenance alert, and Oven Y continues working alone at its constant rate until the order is completed. How many total hours, from 8:00 a.m. until completion, does it take to finish the order?

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Cevap: 9

Cevap

The total time required from 8:00 a.m. to complete the order is 99 hours.
Working together for 22 hours at a combined rate of 18+112=524\frac{1}{8} + \frac{1}{12} = \frac{5}{24} per hour completes 512\frac{5}{12} of the order. The remaining 712\frac{7}{12} of the order takes Oven Y 77 hours to complete at its rate of 112\frac{1}{12} per hour. Adding the initial 22 hours gives a total time of 99 hours.

Adım Adım Çözüm

1
Determine the individual hourly work rates.
Oven X completes 18\frac{1}{8} of the job per hour, and Oven Y completes 112\frac{1}{12} of the job per hour.
Work rate is the reciprocal of the total time required to complete one full job.
2
Calculate the fraction of the job completed in the first 22 hours.
Combined rate is 18+112=524\frac{1}{8} + \frac{1}{12} = \frac{5}{24} job per hour. In 22 hours, they complete 2×524=5122 \times \frac{5}{24} = \frac{5}{12} of the job.
Both ovens work simultaneously for 22 hours before Oven X stops.
3
Determine the remaining fraction of the job.
1512=7121 - \frac{5}{12} = \frac{7}{12} of the job remains.
The full order represents 11 whole unit of work.
4
Find the additional time required for Oven Y to finish the remaining job alone.
Time=7/121/12=7\text{Time} = \frac{7/12}{1/12} = 7 hours.
Time equals remaining work divided by Oven Y's individual work rate.
5
Calculate the total time elapsed from start to completion.
2+7=92 + 7 = 9 hours.
The total time includes the 22 hours of combined work plus the 77 hours Oven Y worked alone.

Anahtar Kavram

Combined Work Rates and Modeling Staggered Work
Soru 48Soru

A technology company manages data storage across three servers: Server X, Server Y, and Server Z. Initially, the amount of data stored on Server Y is 25%25\% greater than the amount stored on Server X, and Server Z stores 4040 gigabytes less data than Server Y. During a system reorganization, the data on Server X increases by 20%20\%, the data on Server Y decreases by 20%20\%, and the data on Server Z increases by 6060 gigabytes. If the total amount of data stored across all three servers after the reorganization is 10%10\% greater than the total initial amount of data, what was the initial amount of data, in gigabytes, stored on Server X?

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Cevap: 160

Cevap

160 gigabytes
Let xx be the initial storage on Server X in gigabytes. Then Server Y initially stores 1.25x1.25x gigabytes and Server Z stores 1.25x401.25x - 40 gigabytes. The initial total storage is T1=x+1.25x+(1.25x40)=3.5x40T_1 = x + 1.25x + (1.25x - 40) = 3.5x - 40. After reorganization, Server X stores 1.20x1.20x, Server Y stores 0.80(1.25x)=1.00x0.80(1.25x) = 1.00x, and Server Z stores (1.25x40)+60=1.25x+20(1.25x - 40) + 60 = 1.25x + 20. The new total storage is T2=1.20x+1.00x+1.25x+20=3.45x+20T_2 = 1.20x + 1.00x + 1.25x + 20 = 3.45x + 20. Since T2T_2 is 10%10\% greater than T1T_1, we have 3.45x+20=1.10(3.5x40)3.45x + 20 = 1.10(3.5x - 40). Expanding the right side gives 3.45x+20=3.85x443.45x + 20 = 3.85x - 44. Rearranging terms yields 0.40x=640.40x = 64, which simplifies to x=160x = 160 gigabytes.

Adım Adım Çözüm

1
Define variables for the initial storage on each server in terms of the initial storage on Server X, xx.
Server X = xx, Server Y = 1.25x1.25x, Server Z = 1.25x401.25x - 40.
Server Y is 25% greater than Server X (1+0.25=1.251 + 0.25 = 1.25), and Server Z is 40 gigabytes less than Server Y.
2
Sum the initial storage values to find the total initial storage T1T_1.
T1=x+1.25x+(1.25x40)=3.5x40T_1 = x + 1.25x + (1.25x - 40) = 3.5x - 40.
Combining like terms gives the overall starting storage equation.
3
Express the storage on each server after the reorganization in terms of xx.
Server X' = 1.20x1.20x, Server Y' = 0.80(1.25x)=1.00x0.80(1.25x) = 1.00x, Server Z' = (1.25x40)+60=1.25x+20(1.25x - 40) + 60 = 1.25x + 20.
Server X increases by 20%, Server Y decreases by 20% of its initial value, and Server Z gains 60 gigabytes.
4
Sum the updated storage values to find the new total storage T2T_2.
T2=1.20x+1.00x+(1.25x+20)=3.45x+20T_2 = 1.20x + 1.00x + (1.25x + 20) = 3.45x + 20.
Adding the three updated amounts gives the new total expression.
5
Set up and solve the equation representing the 10%10\% overall increase (T2=1.10T1T_2 = 1.10 T_1).
3.45x+20=1.10(3.5x40)    3.45x+20=3.85x44    64=0.40x    x=1603.45x + 20 = 1.10(3.5x - 40) \implies 3.45x + 20 = 3.85x - 44 \implies 64 = 0.40x \implies x = 160.
Solving the linear algebraic model yields the value for initial storage on Server X.

Anahtar Kavram

Linear algebraic modeling of dynamic multi-variable systems involving percentage changes.
Tahmini Süre:2m 30s
Soru 49Soru

A logistics company operates a delivery van and a cargo drone along a straight route of 270270 kilometers connecting Hub X and Hub Y. The delivery van departs from Hub X toward Hub Y at a constant speed of 6060 kilometers per hour. Exactly 22 hours later, the cargo drone departs from Hub Y toward Hub X along the same route at a constant speed of 9090 kilometers per hour. How many hours after the delivery van departs will the van and the cargo drone meet?

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Cevap: 3.0 hours

Cevap

3.0 hours
The option specifying '3.0 hours' is correct. During the 2 hours before the drone departs, the van covers 60 km/h×2 h=120 km60 \text{ km/h} \times 2 \text{ h} = 120 \text{ km}. The remaining distance between the vehicles is 270 km120 km=150 km270 \text{ km} - 120 \text{ km} = 150 \text{ km}. Once the drone departs, the two vehicles close the gap at a combined rate of 60+90=150 km/h60 + 90 = 150 \text{ km/h}. The time needed to cover the remaining 150 km150 \text{ km} is 150 km150 km/h=1 hour\frac{150 \text{ km}}{150 \text{ km/h}} = 1 \text{ hour}. Adding the van's initial 22 hours gives a total travel time of 3.03.0 hours.

Adım Adım Çözüm

1
Define variables for travel time and compute distance covered by the van before the drone departs.
In 22 hours at 6060 km/h, the van covers 60×2=12060 \times 2 = 120 kilometers.
The van travels alone for the first two hours.
2
Determine the remaining distance separating the two vehicles when the drone starts moving.
Remaining distance = 270120=150270 - 120 = 150 kilometers.
The total distance between the hubs is 270270 kilometers.
3
Calculate the relative speed of approach and the additional time required to meet.
Combined speed = 60+90=15060 + 90 = 150 km/h. Additional time = 150150=1\frac{150}{150} = 1 hour.
Since the vehicles travel toward each other, their speeds add up.
4
Find the total time elapsed since the van departed.
Total time = 2+1=3.02 + 1 = 3.0 hours.
The question asks for total hours since the van's departure.

Anahtar Kavram

Distance-Rate-Time linear modeling with staggered start times and opposing directions
Tahmini Süre:1m 45s
Soru 50Soru

An investment firm allocated a total principal of $120,000\$120,000 between two accounts, Account X and Account Y. Account X earned a simple annual interest rate of 6%6\%, and Account Y earned a simple annual interest rate of 10%10\%. At the end of one year, the combined total interest earned from both accounts was $9,200\$9,200. An annual administrative fee was then deducted from the interest: a 25%25\% fee on the interest earned from Account X, and a 10%10\% fee on the interest earned from Account Y. What was the net amount of interest, in dollars, remaining after these administrative fees were deducted?

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Cevap: $7,650\$7,650

Cevap

The net amount of interest remaining after administrative fees were deducted is $7,650\$7,650.
The correct answer is $7,650\$7,650. Solving the system x+y=120,000x + y = 120,000 and 0.06x+0.10y=9,2000.06x + 0.10y = 9,200 gives $70,000\$70,000 invested in Account X and $50,000\$50,000 in Account Y. Account X produces $4,200\$4,200 in interest, from which a 25%25\% fee ($1,050\$1,050) is deducted. Account Y produces $5,000\$5,000 in interest, from which a 10%10\% fee ($500\$500) is deducted. Subtracting total fees of $1,550\$1,550 from total interest of $9,200\$9,200 yields $7,650\$7,650.

Adım Adım Çözüm

1
Set up a system of linear equations for the principal amounts invested in Account X and Account Y.
Let xx be the amount invested in Account X and yy be the amount invested in Account Y. The total principal is x+y=120,000x + y = 120,000. The total interest earned is 0.06x+0.10y=9,2000.06x + 0.10y = 9,200.
Modeling the word problem using two variables captures both total principal and total combined interest.
2
Solve the system of equations for xx and yy.
Multiplying x+y=120,000x + y = 120,000 by 0.060.06 gives 0.06x+0.06y=7,2000.06x + 0.06y = 7,200. Subtracting this equation from 0.06x+0.10y=9,2000.06x + 0.10y = 9,200 yields 0.04y=2,0000.04y = 2,000, so y=50,000y = 50,000. Substituting back gives x=70,000x = 70,000.
Determining individual account principals allows calculation of interest generated by each account.
3
Calculate the interest earned from each account and the corresponding administrative fees.
Interest from X = 0.06×70,000=$4,2000.06 \times 70,000 = \$4,200. Interest from Y = 0.10×50,000=$5,0000.10 \times 50,000 = \$5,000. Fee for X = 0.25×4,200=$1,0500.25 \times 4,200 = \$1,050. Fee for Y = 0.10×5,000=$5000.10 \times 5,000 = \$500. Total fees = 1,050+500=$1,5501,050 + 500 = \$1,550.
Each fee rate must be multiplied by the specific interest amount earned by that account.
4
Subtract the total administrative fees from the total interest earned.
Net Interest = $9,200$1,550=$7,650\$9,200 - \$1,550 = \$7,650.
Deducting fees yields the net interest remaining.

Anahtar Kavram

System of Linear Equations for Mixture and Interest Word Problems
Tahmini Süre:2m 0s
Soru 51Soru

A commercial print shop uses two high-speed printing presses, Press Alpha and Press Beta. Press Alpha operates at a constant rate of 120120 pages per minute, while Press Beta operates at a constant rate of 180180 pages per minute. Press Alpha begins printing a job of 15,00015,000 pages at 9:00 AM. At 9:15 AM, Press Beta is turned on to assist Press Alpha, and both presses continue printing simultaneously at their respective constant rates until the job is completed. How many total minutes after 9:00 AM will the entire 15,00015,000-page job be finished?

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Cevap: 59

Cevap

The entire 15,000-page job will be finished 59 minutes after 9:00 AM.
Press Alpha operates alone for the first 15 minutes, completing 15×120=1,80015 \times 120 = 1,800 pages. That leaves 15,0001,800=13,20015,000 - 1,800 = 13,200 pages. Once Press Beta joins at 9:15 AM, the combined rate becomes 120+180=300120 + 180 = 300 pages per minute. The remaining pages require 13,200/300=4413,200 / 300 = 44 minutes. Summing the 15-minute initial period and the 44-minute joint period gives a total of 59 minutes after 9:00 AM.

Adım Adım Çözüm

1
Find the work completed by Press Alpha during the 15-minute staggered start period.
1,800 pages completed.
Press Alpha ran alone for 15 minutes at 120 pages per minute.
2
Determine the remaining work to be done after 9:15 AM.
13,200 pages remaining.
Subtract the completed pages from the total batch size of 15,000 pages.
3
Calculate the combined work rate of Press Alpha and Press Beta.
300 pages per minute.
When working together, rates add linearly: 120 + 180 = 300.
4
Calculate time needed to complete the remaining pages.
44 minutes.
Divide remaining work (13,200 pages) by combined rate (300 pages/min).
5
Calculate total elapsed time from 9:00 AM.
59 minutes.
Combine the 15 initial minutes with the 44 subsequent minutes.

Anahtar Kavram

Linear work-rate equations with staggered initial start times
Tahmini Süre:1m 30s
Soru 52Soru

Two industrial processing units, Unit X and Unit Y, process liquid solution at constant rates of 4040 liters per hour and 6060 liters per hour, respectively. Unit X begins processing a 1,1001,100-liter batch of solution alone. After 55 hours, Unit Y is activated and joins Unit X, working simultaneously at their respective constant rates until the entire batch is completely processed. What is the total time, in hours, from when Unit X started processing until the entire batch was completely processed?

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Cevap: 14

Cevap

14 hours
Unit X works alone for 5 hours, processing 40×5=20040 \times 5 = 200 liters. This leaves 1,100200=9001,100 - 200 = 900 liters of solution remaining. When Unit Y joins, the units process solution at a joint rate of 40+60=10040 + 60 = 100 liters per hour. The remaining 900 liters require 900100=9\frac{900}{100} = 9 hours of combined work. Summing the 5 hours of solo work and 9 hours of combined work gives a total time of 14 hours.

Adım Adım Çözüm

1
Calculate the volume processed by Unit X during its solo operation
40 liters/hour×5 hours=200 liters40 \text{ liters/hour} \times 5 \text{ hours} = 200 \text{ liters}
Unit X operates alone for the first 5 hours at a constant rate of 40 liters per hour.
2
Determine the remaining batch volume to be processed
1,100 liters200 liters=900 liters1,100 \text{ liters} - 200 \text{ liters} = 900 \text{ liters}
Subtract the volume already completed from the total batch size.
3
Calculate the combined processing rate of Unit X and Unit Y
40 liters/hour+60 liters/hour=100 liters/hour40 \text{ liters/hour} + 60 \text{ liters/hour} = 100 \text{ liters/hour}
Both units work together simultaneously after the first 5 hours.
4
Find the time needed for both units to process the remaining volume
900 liters100 liters/hour=9 hours\frac{900 \text{ liters}}{100 \text{ liters/hour}} = 9 \text{ hours}
Divide the remaining volume by the combined rate.
5
Calculate the total elapsed time from the start
5 hours (solo)+9 hours (combined)=14 hours5 \text{ hours (solo)} + 9 \text{ hours (combined)} = 14 \text{ hours}
Add the initial solo work time to the combined work time.

Anahtar Kavram

Algebraic modeling of combined work rates with staggered start times
Tahmini Süre:1m 30s
Soru 53Soru

A cyclist travels from City XX to City YY at a constant speed of 2424 miles per hour. On the return trip from City YY to City XX along the exact same route, adverse weather conditions reduce the cyclist's average speed by 25%25\%. If the total time for the entire round trip is 77 hours, what is the distance, in miles, between City XX and City YY?

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Cevap: 7272

Cevap

The distance between City XX and City YY is 7272 miles.
To find the one-way distance dd, first calculate the return speed: 24×0.75=1824 \times 0.75 = 18 mph. Express the total time spent traveling as the sum of the time for each leg: d24+d18=7\frac{d}{24} + \frac{d}{18} = 7. Combining the fractions over a common denominator of 7272 gives 7d72=7\frac{7d}{72} = 7, which simplifies to d=72d = 72 miles.

Adım Adım Çözüm

1
Determine the return speed
Return speed = 24×(10.25)=1824 \times (1 - 0.25) = 18 miles per hour.
Adverse weather reduces the outbound speed of 2424 mph by 25%25\%.
2
Formulate the total time equation in terms of distance dd
d24+d18=7\frac{d}{24} + \frac{d}{18} = 7
Time equals distance divided by rate. The sum of the outbound time and return time is 77 hours.
3
Solve the algebraic equation for dd
\frac{3d + 4d}{72} = 7 \implies \frac{7d}{72} = 7 \implies d = 72
Finding a common denominator of 7272 allows combining the fractional time expressions.

Anahtar Kavram

Distance, Rate, and Time Word Problems
Tahmini Süre:1m 30s
Soru 54Soru

A theater sells student tickets for $20\$20 each and adult tickets for $35\$35 each. For a specific performance, the theater sold a total of 150150 tickets and collected total revenue of RR dollars. If at least 4040 student tickets were sold and at most 9090 adult tickets were sold, which of the following values could be the total revenue RR? Select all such values.

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Cevap: $3450\$3{}450; $4200\$4{}200

Cevap

The possible values for the total revenue RR are $3450\$3{}450 and $4200\$4{}200.
The linear revenue model is R=525015sR = 5250 - 15s. Considering both conditions (s40s \ge 40 and a=150s90    s60a = 150 - s \le 90 \implies s \ge 60), the valid range for student tickets is 60s15060 \le s \le 150. This restricts the possible revenue RR to multiples of $15\$15 between $3000\$3{}000 and $4350\$4{}350. Both $3450\$3{}450 and $4200\$4{}200 fall within this valid range and correspond to integer ticket quantities (s=120,a=30s = 120, a = 30 and s=70,a=80s = 70, a = 80, respectively).

Adım Adım Çözüm

1
Set up equations for the total number of tickets and revenue.
Let ss be the number of student tickets and aa be the number of adult tickets. Then s+a=150s + a = 150, so a=150sa = 150 - s. Total revenue R=20s+35a=20s+35(150s)=525015sR = 20s + 35a = 20s + 35(150 - s) = 5250 - 15s.
Expressing revenue in terms of a single variable ss simplifies finding the domain and range.
2
Determine the constraints on the variable ss.
We are given s40s \ge 40 and a90a \le 90. Substituting a=150s90a = 150 - s \le 90 yields s60s \ge 60. Combining constraints gives 60s15060 \le s \le 150.
The number of adult tickets being at most 9090 forces the number of student tickets to be at least 6060.
3
Calculate the upper and lower bounds for the revenue RR.
Maximum revenue occurs when s=60s = 60: Rmax=525015(60)=$4350R_{\text{max}} = 5250 - 15(60) = \$4{}350. Minimum revenue occurs when s=150s = 150: Rmin=525015(150)=$3000R_{\text{min}} = 5250 - 15(150) = \$3{}000.
Since R=525015sR = 5250 - 15s is a decreasing linear function of ss, the maximum revenue occurs at the minimum valid value of ss and vice versa.
4
Evaluate the given choices against the range and divisibility requirements.
RR must be an integer multiple of 1515 subtracted from 52505250, meaning RR must be between $3000\$3{}000 and $4350\$4{}350 inclusive, and (5250R)(5250 - R) must be divisible by 1515. $3450\$3{}450 (where s=120s = 120) and $4200\$4{}200 (where s=70s = 70) are both valid. $2850\$2{}850 is below the minimum bound, $4400\$4{}400 does not yield an integer value for ss, and $4650\$4{}650 violates the adult ticket upper bound.
Only options meeting both inequality constraints and integer ticket requirements are valid.

Anahtar Kavram

Linear modeling of word problems under linear system constraints and inequalities
Tahmini Süre:1m 30s
Soru 55Soru

A clean energy technology company manufactures two models of solar panels: Model X and Model Y. Model X produces 150150 kilowatt-hours (kWh) of electricity per day and costs $400\$400 to manufacture, while Model Y produces 200200 kWh of electricity per day and costs $550\$550 to manufacture. A solar energy project purchased a total of 5050 panels for a total manufacturing cost of $24,500\$24,500. What is the total daily electricity production, in kilowatt-hours, of all 5050 panels combined?

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Cevap: 9,0009,000

Cevap

The total daily electricity production of all 5050 panels combined is 9,0009,000 kWh.
The correct option is 9,0009,000 kWh. Defining xx as the number of Model X panels and yy as the number of Model Y panels gives the equations x+y=50x + y = 50 and 400x+550y=24,500400x + 550y = 24,500. Substituting y=50xy = 50 - x yields 400x+550(50x)=24,500400x + 550(50 - x) = 24,500, which simplifies to 150x=3,000-150x = -3,000, so x=20x = 20 and y=30y = 30. Computing the total output yields 20(150)+30(200)=3,000+6,000=9,00020(150) + 30(200) = 3,000 + 6,000 = 9,000 kWh.

Adım Adım Çözüm

1
Define variables for the quantities of each panel model.
Let xx represent the number of Model X panels and yy represent the number of Model Y panels.
Establishing explicit variables allows formulating a system of linear equations from the word problem.
2
Set up equations for total panel quantity and total manufacturing cost.
System equations: x+y=50x + y = 50 and 400x+550y=24,500400x + 550y = 24,500.
The total number of panels is 5050, and the combined manufacturing cost equals $24,500\$24,500.
3
Solve the system using substitution.
Substitute y=50xy = 50 - x into the cost equation: 400x+550(50x)=24,500    400x+27,500550x=24,500    150x=3,000    x=20400x + 550(50 - x) = 24,500 \implies 400x + 27,500 - 550x = 24,500 \implies -150x = -3,000 \implies x = 20. Consequently, y=5020=30y = 50 - 20 = 30.
Determining x=20x = 20 and y=30y = 30 gives the exact number of Model X and Model Y panels purchased.
4
Calculate the total daily electricity production.
Total production =20(150)+30(200)=3,000+6,000=9,000= 20(150) + 30(200) = 3,000 + 6,000 = 9,000 kWh.
Multiply the quantity of each panel model by its respective daily output rate and sum the products.

Anahtar Kavram

Formulating and solving a system of two linear equations from a real-world scenario to find unknown quantities and evaluate a secondary combination function.
Tahmini Süre:1m 30s
Soru 56Soru

A courier service calculates the shipping cost for a package based on its weight ww, in pounds. For packages weighing up to 2020 pounds, the cost is a flat fee of $12.00\$12.00 plus $2.50\$2.50 per pound. For packages weighing more than 2020 pounds, the cost is a flat fee of $20.00\$20.00 plus $2.00\$2.00 per pound. If the total shipping cost for a package was strictly greater than $45.00\$45.00 and at most $70.00\$70.00, which of the following could be the weight of the package, in pounds? Select all such weights.

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Cevap: 1515 pounds; 2020 pounds; 2424 pounds

Cevap

The valid weights of the package are 15 pounds, 20 pounds, and 24 pounds.
The weight of the package must result in a total cost C(w)C(w) such that $45.00<C(w)$70.00\$45.00 < C(w) \le \$70.00. Evaluating the options:
- For 15 pounds: 12+2.50(15)=$49.5012 + 2.50(15) = \$49.50, which falls within the range.
- For 20 pounds: 12+2.50(20)=$62.0012 + 2.50(20) = \$62.00, which falls within the range.
- For 24 pounds: 20+2.00(24)=$68.0020 + 2.00(24) = \$68.00, which falls within the range.

Adım Adım Çözüm

1
Formulate the cost function C(w)C(w) as a piecewise model.
C(w)=12+2.50wC(w) = 12 + 2.50w for 0<w200 < w \le 20, and C(w)=20+2.00wC(w) = 20 + 2.00w for w>20w > 20.
The cost structure changes depending on whether the weight exceeds 2020 pounds.
2
Set up and solve the inequality 45<C(w)7045 < C(w) \le 70 for packages up to 2020 pounds.
45<12+2.50w70    33<2.50w58    13.2<w23.245 < 12 + 2.50w \le 70 \implies 33 < 2.50w \le 58 \implies 13.2 < w \le 23.2. Restricting to w20w \le 20 gives 13.2<w2013.2 < w \le 20.
This determines the valid weight interval for packages billed under the first tier.
3
Set up and solve the inequality 45<C(w)7045 < C(w) \le 70 for packages over 2020 pounds.
45<20+2.00w70    25<2.00w50    12.5<w2545 < 20 + 2.00w \le 70 \implies 25 < 2.00w \le 50 \implies 12.5 < w \le 25. Restricting to w>20w > 20 gives 20<w2520 < w \le 25.
This determines the valid weight interval for packages billed under the second tier.
4
Combine the valid intervals and evaluate each option.
The overall valid weight interval is 13.2<w2513.2 < w \le 25. Testing the values: 12 pounds is outside the range; 15 pounds, 20 pounds, and 24 pounds are within the range; 26 pounds is outside the range.
Any weight strictly greater than 13.213.2 pounds and up to 2525 pounds produces a cost between $45.00\$45.00 and $70.00\$70.00.

Anahtar Kavram

Algebraic Modeling of Piecewise Functions and Compound Inequalities
Soru 57Soru

A logistics company operates two delivery vans, Van A and Van B. Van A consumes fuel at a rate of 11 gallon for every 1515 miles driven, and Van B consumes fuel at a rate of 11 gallon for every 2525 miles driven. On a specific trip, the two vans were driven a total combined distance of 450450 miles and together consumed exactly 2222 gallons of fuel. What was the total distance, in miles, driven by Van A?

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Cevap: 150 miles

Cevap

The total distance driven by Van A was 150 miles.
The correct answer is 150 miles. By setting up the total fuel consumption equation as dA15+450dA25=22\frac{d_A}{15} + \frac{450 - d_A}{25} = 22, multiplying by the least common multiple 7575 gives 5dA+13503dA=16505d_A + 1350 - 3d_A = 1650, which simplifies to 2dA=3002d_A = 300 and dA=150d_A = 150 miles.

Adım Adım Çözüm

1
Define variables for the distance traveled by each van.
Let dAd_A be the distance driven by Van A. Then the distance driven by Van B is 450dA450 - d_A.
The total combined distance for both vans is 450450 miles.
2
Express the total fuel consumed in terms of dAd_A.
\frac{d_A}{15} + \frac{450 - d_A}{25} = 22
Fuel used equals distance divided by miles per gallon for each vehicle.
3
Clear denominators by multiplying the entire equation by the common denominator 75.
5d_A + 3(450 - d_A) = 1650
Simplifies fractions to solve the linear algebraic equation easily.
4
Solve for dAd_A.
5d_A + 1350 - 3d_A = 1650 \implies 2d_A = 300 \implies d_A = 150
Isolates the target variable dAd_A to find the distance driven by Van A.

Anahtar Kavram

Linear Equations and Rate-Distance Modeling
Soru 58Soru

A laboratory technician has 1212 liters of a solution containing 15%15\% salt by weight. The technician wants to increase the salt concentration to 25%25\% by adding a second solution that contains 40%40\% salt by weight. How many liters of the 40%40\% solution must be added?

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Cevap: 8

Cevap

8 liters of the 40% solution must be added.
The total amount of salt contributed by the two solutions is 0.15(12)+0.40x=1.8+0.40x0.15(12) + 0.40x = 1.8 + 0.40x. The final mixture volume is (12+x)(12 + x) liters, and its concentration must be 25%25\%. Equating the total salt to 25%25\% of total volume yields 1.8+0.40x=0.25(12+x)1.8 + 0.40x = 0.25(12 + x). Expanding gives 1.8+0.40x=3.0+0.25x1.8 + 0.40x = 3.0 + 0.25x, which simplifies to 0.15x=1.20.15x = 1.2, giving x=8x = 8 liters.

Adım Adım Çözüm

1
Define the unknown variable and calculate the initial solute quantity.
Let xx be the volume of the 40%40\% solution added (in liters). Salt in initial solution = 0.15×12=1.80.15 \times 12 = 1.8 liters.
Establishing the mass balance of the salt solute is necessary to construct the algebraic equation.
2
Set up the algebraic concentration equation.
1.8+0.40x=0.25(12+x)1.8 + 0.40x = 0.25(12 + x)
The combined salt from both solutions must equal 25%25\% of the total combined liquid volume (12+x)(12 + x) liters.
3
Solve the linear equation for xx.
1.8+0.40x=3.0+0.25x    0.15x=1.2    x=81.8 + 0.40x = 3.0 + 0.25x \implies 0.15x = 1.2 \implies x = 8
Isolating xx yields the exact number of liters required.

Anahtar Kavram

Algebraic mixture problems using mass balance equations.
Tahmini Süre:1m 30s
Soru 59Soru

A municipal water treatment facility uses two intake pipes, Pipe XX and Pipe YY, to fill a main reservoir. Operating alone at its constant rate, Pipe XX can fill the empty reservoir in 1010 hours. Operating alone at its constant rate, Pipe YY can fill the empty reservoir in 1515 hours. Pipe XX is turned on first and operates alone for 33 hours. Then, Pipe YY is also turned on, and both pipes operate together until the reservoir is completely full. What is the total number of hours Pipe XX operates from the moment it is turned on until the reservoir is completely filled?

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Cevap: 7.27.2

Cevap

The total number of hours Pipe X operates is 7.27.2 hours.
The correct answer is 7.27.2 hours. Pipe X completes 3/103/10 of the reservoir in 3 hours, leaving 7/107/10 of the reservoir to be filled. The combined rate of Pipe X and Pipe Y is 1/10+1/15=1/61/10 + 1/15 = 1/6 per hour. The joint time required to fill the remaining 7/107/10 is (7/10)/(1/6)=4.2(7/10) / (1/6) = 4.2 hours. Adding the initial 3 hours Pipe X worked alone yields a total of 3+4.2=7.23 + 4.2 = 7.2 hours.

Adım Adım Çözüm

1
Determine the individual hourly work rates of Pipe X and Pipe Y.
Rate of Pipe X = 110\frac{1}{10} reservoir per hour; Rate of Pipe Y = 115\frac{1}{15} reservoir per hour.
The rate is the reciprocal of the total time required to complete the job individually.
2
Calculate the fraction of the reservoir filled by Pipe X during its initial 3-hour solo operation.
Work done in first 3 hours = 3×110=3103 \times \frac{1}{10} = \frac{3}{10} of the reservoir.
Multiplying Pipe X's rate by its solo operating time gives the completed portion of the work.
3
Find the remaining fraction of the reservoir that needs to be filled.
Remaining work = 1310=7101 - \frac{3}{10} = \frac{7}{10} of the reservoir.
Subtracting the completed portion from the whole (1) leaves the uncompleted portion.
4
Determine the combined hourly rate when both pipes operate simultaneously.
Combined rate = 110+115=330+230=530=16\frac{1}{10} + \frac{1}{15} = \frac{3}{30} + \frac{2}{30} = \frac{5}{30} = \frac{1}{6} of the reservoir per hour.
Simultaneous operation rates are additive.
5
Calculate the time tt during which both pipes operate together to finish the remaining work.
t=71016=710×6=4210=4.2t = \frac{\frac{7}{10}}{\frac{1}{6}} = \frac{7}{10} \times 6 = \frac{42}{10} = 4.2 hours.
Dividing the remaining work by the combined rate yields the joint operation time.
6
Add Pipe X's solo time to the joint operation time to get Pipe X's total operating time.
Total time = 3+4.2=7.23 + 4.2 = 7.2 hours.
Pipe X was active during both the initial solo period and the joint operating period.

Anahtar Kavram

Combined Rate and Staggered Work Modeling
Tahmini Süre:2m 0s
Soru 60Soru

An investor allocated a total principal of $10,000\$10,000 between two accounts, Account X and Account Y. Account X pays simple annual interest at a rate of 6%6\%, while Account Y pays simple annual interest at a rate of 8%8\%. Let xx represent the amount of money, in dollars, invested in Account X, and let dd represent the total annual interest earned, in dollars, from both accounts after one year. Which of the following statements must be true? Select all that apply.

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Cevap: The total annual interest dd satisfies 600d800600 \le d \le 800.; The amount invested in Account X can be represented as x=800d0.02x = \frac{800 - d}{0.02}.; If equal amounts were invested in both accounts, the total annual interest earned is $700\$700.

Cevap

The true statements are that the total annual interest dd satisfies 600d800600 \le d \le 800, the amount in Account X is given by x=800d0.02x = \frac{800 - d}{0.02}, and equal investment in both accounts yields $700\$700 in total interest.
The total interest equation d=8000.02xd = 800 - 0.02x dictates all valid relationships. Because 0x10,0000 \le x \le 10,000, the bounds for dd are strictly between 600600 and 800800. Rearranging the equation yields x=800d0.02x = \frac{800 - d}{0.02}, which correctly models the Account X investment. Substituting x=5,000x = 5,000 yields d=700d = 700, confirming the equal-allocation scenario.

Adım Adım Çözüm

1
Formulate the total interest model as a linear equation in terms of xx.
d=0.06x+0.08(10,000x)=8000.02xd = 0.06x + 0.08(10,000 - x) = 800 - 0.02x
The interest earned from Account X is 0.06x0.06x and the interest from Account Y is 0.08(10,000x)0.08(10,000 - x).
2
Determine the range of possible interest values for 0x10,0000 \le x \le 10,000.
When x=10,000x = 10,000, d=600d = 600. When x=0x = 0, d=800d = 800. Thus 600d800600 \le d \le 800.
The minimum and maximum interest values occur at the extreme allocation bounds.
3
Rearrange the interest equation to express xx in terms of dd.
0.02x=800d    x=800d0.020.02x = 800 - d \implies x = \frac{800 - d}{0.02}
Isolating xx provides a formula for calculating the Account X principal directly from the total interest.
4
Evaluate the specific numerical cases given in the options.
Equal investment (x=5,000x = 5,000) gives d=800100=700d = 800 - 100 = 700. For d=750d = 750, x=2,500x = 2,500 (Account Y = 7,5007,500). For d=680d = 680, x=6,000x = 6,000 (Account Y = 4,0004,000, ratio 3:23:2).
Substituting specific values tests the validity of each conditional statement.

Anahtar Kavram

Linear Modeling and Algebraic Rate Allocation
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