Arithmetic

306 soru

Soru 201Soru

Pipes AA and BB, operating together at their respective constant rates, can fill an empty storage tank in 66 hours. Pipes BB and CC, operating together at their constant rates, can fill the same tank in 88 hours. The rate at which Pipe AA fills the tank is 1.51.5 times the rate at which Pipe CC fills the tank. If all three pipes operate together for 33 hours to fill the empty tank, after which Pipe BB is closed, how many additional hours will it take for Pipes AA and CC together to finish filling the tank?

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Cevap: 65\frac{6}{5}

Cevap

65\frac{6}{5} hours
The rate equations established from the problem yield individual rates of 18\frac{1}{8} tank/hr for Pipe AA, 124\frac{1}{24} tank/hr for Pipe BB, and 112\frac{1}{12} tank/hr for Pipe CC. Working together for 33 hours at a combined rate of 14\frac{1}{4} tank/hr, all three pipes fill 34\frac{3}{4} of the tank, leaving 14\frac{1}{4} of the capacity to be filled. After Pipe BB closes, Pipes AA and CC work at a combined rate of 18+112=524\frac{1}{8} + \frac{1}{12} = \frac{5}{24} tank/hr. Dividing the remaining 14\frac{1}{4} tank by 524\frac{5}{24} tank/hr gives 65\frac{6}{5} hours.

Adım Adım Çözüm

1
Express given conditions in terms of work rates per hour (rA,rB,rCr_A, r_B, r_C).
rA+rB=16r_A + r_B = \frac{1}{6}, rB+rC=18r_B + r_C = \frac{1}{8}, and rA=1.5rC=32rCr_A = 1.5 r_C = \frac{3}{2} r_C.
Filling a full tank in HH hours means completing 1H\frac{1}{H} of the tank per hour.
2
Solve the system of equations for individual rates rA,rB,rCr_A, r_B, r_C.
Substituting rB=18rCr_B = \frac{1}{8} - r_C into rA+rB=16r_A + r_B = \frac{1}{6} yields 32rC+18rC=16    12rC=124    rC=112\frac{3}{2} r_C + \frac{1}{8} - r_C = \frac{1}{6} \implies \frac{1}{2} r_C = \frac{1}{24} \implies r_C = \frac{1}{12}. Consequently, rA=18r_A = \frac{1}{8} and rB=124r_B = \frac{1}{24}.
Finding individual unit rates allows calculating any combined work scenario.
3
Calculate the fraction of the tank filled in the first 3 hours with all three pipes open.
Combined rate rA+rB+rC=18+124+112=3+1+224=624=14r_A + r_B + r_C = \frac{1}{8} + \frac{1}{24} + \frac{1}{12} = \frac{3+1+2}{24} = \frac{6}{24} = \frac{1}{4} of the tank per hour. In 33 hours, 3×14=343 \times \frac{1}{4} = \frac{3}{4} of the tank is filled, leaving 134=141 - \frac{3}{4} = \frac{1}{4} of the tank empty.
Work completed equals rate multiplied by time.
4
Determine the additional time needed for Pipes AA and CC to fill the remaining 14\frac{1}{4} of the tank.
Combined rate of AA and CC is rA+rC=18+112=524r_A + r_C = \frac{1}{8} + \frac{1}{12} = \frac{5}{24} per hour. Additional time t=14524=14×245=65t = \frac{\frac{1}{4}}{\frac{5}{24}} = \frac{1}{4} \times \frac{24}{5} = \frac{6}{5} hours.
Time required equals remaining work divided by active rate.

Anahtar Kavram

Combined Work Rates and Systems of Rate Equations
Soru 202Soru

If xx and yy are positive integers such that 2x2y=19202^x - 2^y = 1920, what is the value of x+yx + y?

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Cevap: 1818

Cevap

The correct value is 18.
Factoring 2y2^y from 2x2y2^x - 2^y yields 2y(2xy1)2^y(2^{x-y} - 1). Factoring 1920 as 27×152^7 \times 15 allows us to uniquely match the power-of-two factor 2y=272^y = 2^7 (y=7y = 7) and the odd factor 2xy1=152^{x-y} - 1 = 15 (xy=4    x=11x - y = 4 \implies x = 11). Summing xx and yy gives 11+7=1811 + 7 = 18.

Adım Adım Çözüm

1
Factor out the smaller power of 2 from the expression
2y(2xy1)=19202^y(2^{x-y} - 1) = 1920
Since xx and yy are positive integers and 2x2y>02^x - 2^y > 0, we know x>yx > y. Factoring 2y2^y separates the even power of 2 component from an odd component.
2
Determine the prime factorization of 1920 into a power of 2 and an odd integer
1920=128×15=27×151920 = 128 \times 15 = 2^7 \times 15
Repeatedly dividing 1920 by 2 gives 1920=27×151920 = 2^7 \times 15, where 15 is an odd integer.
3
Equate the even and odd components
2y=27    y=72^y = 2^7 \implies y = 7 and 2xy1=15    2xy=16=24    xy=42^{x-y} - 1 = 15 \implies 2^{x-y} = 16 = 2^4 \implies x - y = 4
Because xy1x - y \ge 1, the quantity 2xy12^{x-y} - 1 must be an odd integer, forcing it to equal 15 and the power of 2 factor to equal 272^7.
4
Solve for xx and calculate the final sum x+yx + y
x=7+4=11x = 7 + 4 = 11, so x+y=11+7=18x + y = 11 + 7 = 18
Adding x=11x = 11 and y=7y = 7 gives the required value.

Anahtar Kavram

Factoring exponential expressions by pulling out the common base power and matching unique prime factorizations.
Soru 203Soru

An investor allocates a total principal of $10,000\$10,000 between two investment options, Account X and Account Y. Account X earns simple interest at an annual rate of 8%8\%. Account Y earns interest at an annual rate of 8%8\% compounded semi-annually. Neither account receives additional deposits or withdrawals for a period of 22 years. Which of the following statements MUST be true?

Select all such statements.

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Cevap: If the total principal is divided equally between Account X and Account Y, the total interest earned after 22 years is greater than $1,640\$1,640.; Allocating a greater portion of the total principal to Account Y strictly increases the total interest earned after 22 years.

Cevap

The correct statements are the statement regarding equal division yielding total interest greater than $1,640, and the statement that allocating a greater portion of principal to Account Y increases the total interest earned.
The statement regarding equal principal division is true because 5,000placedinAccountXyields5,000 placed in Account X yields 800 in simple interest and 5,000placedinAccountYyields5,000 placed in Account Y yields 849.29 under semi-annual compounding, giving a sum of 1,649.29whichexceeds1,649.29 which exceeds 1,640. The statement regarding shifting allocation to Account Y is true because Account Y's effective two-year yield of 16.99% is higher than Account X's two-year simple yield of 16.00%.

Adım Adım Çözüm

1
Calculate the effective 2-year return for Account X under simple interest.
Simple interest over 2 years at an annual rate of 8% is 2×8%=16%2 \times 8\% = 16\%. Total return factor is 0.160.16.
Simple interest accumulates linearly as I=PrtI = P \cdot r \cdot t.
2
Calculate the effective 2-year return for Account Y under semi-annual compound interest.
Semi-annual rate is 8%2=4%=0.04\frac{8\%}{2} = 4\% = 0.04. The number of compounding periods in 2 years is 2×2=42 \times 2 = 4. Total compound multiplier is (1.04)4=1.16985856(1.04)^4 = 1.16985856. Thus, the total interest earned is 16.985856%16.985856\% of the principal.
Compound interest uses the period rate raised to the power of total compounding periods: (1+rperiod)n(1 + r_{period})^n.
3
Evaluate the statement for equal division of $10,000.
With 5,000inAccountX:interest=5,000 in Account X: interest = 5,000 \times 0.16 = 800.With800. With 5,000 in Account Y: interest = 5,000×0.169858565,000 \times 0.16985856 \approx 849.29. Total interest = 800+800 + 849.29 = 1,649.29.Since1,649.29. Since 1,649.29 > $1,640, this statement is TRUE.
Summing the interest from both accounts confirms the total exceeds $1,640.
4
Evaluate the statement comparing allocation shifts.
Since Account Y earns approximately 16.99%16.99\% over 2 years and Account X earns 16.00%16.00\%, the yield of Y exceeds X by approximately 0.99%0.99\%. Thus, increasing the allocation to Account Y increases overall interest earned. This statement is TRUE.
Reallocating principal to an option with a higher effective yield strictly increases overall earnings.
5
Evaluate the statement for placing all funds in Account X.
If all 10,000isinAccountX,interest=10,000 is in Account X, interest = 10,000 \times 0.16 = 1,600.Theclaimof1,600. The claim of 1,664 is FALSE.
1,664resultsfromcalculatingannualcompoundinterest(1,664 results from calculating annual compound interest ( 10,000 \times (1.08^2 - 1)$), which does not apply to simple interest.

Anahtar Kavram

Simple Interest vs. Compound Interest
Tahmini Süre:2m 0s
Soru 204Soru

A rectangular floor measuring 126 cm126\text{ cm} by 180 cm180\text{ cm} is to be completely covered with identical square tiles of the largest possible side length, without cutting any tiles or leaving gaps. What is the total number of square tiles required to cover the floor?

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Cevap: 70

Cevap

The total number of square tiles required is 70.
To cover the rectangular floor with the largest possible identical square tiles, the side length of the square tile must be the greatest common divisor of 126126 and 180180. Factoring both numbers gives 126=2×32×7126 = 2 \times 3^2 \times 7 and 180=22×32×5180 = 2^2 \times 3^2 \times 5. The greatest common divisor is 2×32=18 cm2 \times 3^2 = 18\text{ cm}. Dividing the dimensions by 18 cm18\text{ cm} gives 77 tiles along the length and 1010 tiles along the width. Multiplying 7×107 \times 10 yields a total of 7070 tiles.

Adım Adım Çözüm

1
Find the prime factorization of both dimensions of the floor.
126=21×32×71126 = 2^1 \times 3^2 \times 7^1 and 180=22×32×51180 = 2^2 \times 3^2 \times 5^1
Prime factorization allows systematic determination of the greatest common divisor.
2
Calculate the Greatest Common Divisor (GCD) of 126 and 180 to determine the largest possible square tile side length.
gcd(126,180)=21×32=18 cm\gcd(126, 180) = 2^1 \times 3^2 = 18\text{ cm}
The square tiles must fit evenly along both the length and width without cutting.
3
Determine the number of tiles along each dimension.
Along length: 126÷18=7126 \div 18 = 7; along width: 180÷18=10180 \div 18 = 10
Dividing each total length by the tile side length gives the tile count per side.
4
Calculate the total number of tiles required.
7×10=70 tiles7 \times 10 = 70\text{ tiles}
The floor forms a 7 by 10 grid of tiles.

Anahtar Kavram

Greatest Common Divisor (GCD) applications in geometric tiling
Soru 205Soru

Three industrial machines, XX, YY, and ZZ, continuously produce liquid chemical mixtures composed solely of Compounds AA and BB.

- Machine XX produces the mixture at a constant rate of 100100 liters per hour, with Compound AA and Compound BB in a ratio of 3:23:2 by volume.
- Machine YY produces the mixture at a constant rate of 150150 liters per hour, with Compound AA and Compound BB in a ratio of 1:41:4 by volume.
- Machine ZZ produces the mixture at a constant rate of RR liters per hour, with Compound AA and Compound BB in a ratio of 7:37:3 by volume.

If all three machines operate simultaneously for 44 hours, the resulting combined mixture contains equal total volumes of Compound AA and Compound BB.

Which of the following statements must be true? Select all that apply.

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Cevap: The operating rate RR of Machine ZZ is 175175 liters per hour.; Machine ZZ accounts for more than 40%40\% of the total volume of the combined mixture produced in 44 hours.; In the 4-hour output, the volume of Compound BB produced by Machine YY is greater than the total volume of Compound BB produced by Machines XX and ZZ combined.

Cevap

The statements asserting that Machine Z's rate is 175 liters per hour, that Machine Z accounts for over 40% of the total output volume, and that Machine Y produces more Compound B than Machines X and Z combined are all true.
The correct options are those stating that Machine Z operates at 175 liters per hour, that Machine Z accounts for over 40% of the 4-hour output, and that Machine Y produces more Compound B than Machines X and Z combined. Machine X produces 240 liters of Compound A and 160 liters of Compound B in 4 hours. Machine Y produces 120 liters of Compound A and 480 liters of Compound B in 4 hours. Machine Z produces 2.8R liters of Compound A and 1.2R liters of Compound B in 4 hours. Equating total Compound A (360 + 2.8R) to total Compound B (640 + 1.2R) gives 1.6R = 280, so R = 175 liters per hour. Machine Z thus contributes 700 liters out of 1700 total liters, which is approximately 41.18% (greater than 40%). Machine Y produces 480 liters of Compound B, which exceeds the 370 liters of Compound B produced by Machines X and Z combined (160 + 210 liters).

Adım Adım Çözüm

1
Calculate the volumes of Compound A and Compound B produced by Machines X and Y in 4 hours.
Machine X produces 400400 L total (240240 L of A, 160160 L of B). Machine Y produces 600600 L total (120120 L of A, 480480 L of B). Combined from X and Y: 360360 L of A and 640640 L of B.
Decompose each machine's total 4-hour output into individual compound amounts using part-to-whole fraction multipliers.
2
Formulate Machine Z's 4-hour output expressions and solve for rate R.
Machine Z produces 4R4R L total (2.8R2.8R L of A, 1.2R1.2R L of B). Setting total A equal to total B: 360+2.8R=640+1.2R    1.6R=280    R=175360 + 2.8R = 640 + 1.2R \implies 1.6R = 280 \implies R = 175 L/hr.
The condition of equal total volumes of Compound A and Compound B forms a single linear equation in terms of R.
3
Determine Machine Z's proportion of the total volume produced by all three machines.
Machine Z volume = 4×175=7004 \times 175 = 700 L. Total volume = 400+600+700=1700400 + 600 + 700 = 1700 L. Percentage = 7001700×100%41.18%>40%\frac{700}{1700} \times 100\% \approx 41.18\% > 40\%.
Evaluate whether Machine Z contributes more than 40% of the complete 1700-liter mixture.
4
Compare Compound B output from Machine Y against the combined Compound B output from X and Z.
Machine Y produces 480480 L of B. Machines X and Z produce 160+(1.2×175)=370160 + (1.2 \times 175) = 370 L of B. 480>370480 > 370 is true.
Direct numerical comparison verifies the inequality statement.
5
Evaluate the remaining ratio claims.
Compound A ratio X to Z is 240:490=24:492:3240 : 490 = 24 : 49 \neq 2 : 3. Combined X and Z ratio of A to B is 730:370=73:377:3730 : 370 = 73 : 37 \neq 7 : 3. Both claims are false.
Check remaining distractors for mathematical accuracy.

Anahtar Kavram

Multi-rate and multi-component ratio mixture balancing
Soru 206Soru

If xx and yy are real numbers such that 1<x<0<y<1-1 < x < 0 < y < 1, which of the following statements MUST be true? Select all such statements.

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Cevap: x3<x5x^3 < x^5; (y1/2)x>1\left(y^{1/2}\right)^x > 1

Cevap

The statements x3<x5x^3 < x^5 and (y1/2)x>1\left(y^{1/2}\right)^x > 1 MUST be true.
For 1<x<0<y<1-1 < x < 0 < y < 1, odd powers of xx satisfy 1<x<x3<x5<0-1 < x < x^3 < x^5 < 0, making the inequality comparing x3x^3 and x5x^5 true. Furthermore, y1/2y^{1/2} lies in (0,1)(0, 1), and raising a base in (0,1)(0, 1) to a negative exponent xx produces a result strictly greater than 1.

Adım Adım Çözüm

1
Analyze the odd power inequality x3<x5x^3 < x^5 for 1<x<0-1 < x < 0.
Since x(1,0)x \in (-1, 0), x2(0,1)x^2 \in (0, 1). Multiplying 1<x<0-1 < x < 0 by x2x^2 gives x<x3<x5<0x < x^3 < x^5 < 0. Thus, x3<x5x^3 < x^5 holds.
Odd powers preserve negative signs, and higher powers of fractions between 0 and 1 have smaller absolute values.
2
Evaluate the principal square root x2\sqrt{x^2}.
By definition, x2=x\sqrt{x^2} = |x|. Since x<0x < 0, x=xx|x| = -x \neq x.
The principal square root of a real number is always non-negative.
3
Analyze the expression (y1/2)x\left(y^{1/2}\right)^x.
Since 0<y<10 < y < 1, 0<y1/2<10 < y^{1/2} < 1. Let k=y1/2k = y^{1/2}. Then kx=(1k)xk^x = \left(\frac{1}{k}\right)^{-x}. Since k<1k < 1, 1k>1\frac{1}{k} > 1, and since x<0x < 0, x>0-x > 0. A base greater than 1 raised to a positive power is greater than 1.
Negative exponents indicate the reciprocal of the base.
4
Evaluate (x+y)2=x2+y2(x + y)^2 = x^2 + y^2.
(x+y)2=x2+2xy+y2(x + y)^2 = x^2 + 2xy + y^2. Because x<0x < 0 and y>0y > 0, 2xy<02xy < 0, so (x+y)2<x2+y2(x + y)^2 < x^2 + y^2.
Exponents do not distribute over addition, and cross-terms must be accounted for.
5
Evaluate x4>x2x^4 > x^2.
For 1<x<0-1 < x < 0, 0<x2<10 < x^2 < 1. Squaring a number in (0,1)(0, 1) yields a smaller number, so x4<x2x^4 < x^2.
Higher even powers of quantities with magnitude less than 1 decrease in magnitude.

Anahtar Kavram

Properties of exponents, fractional powers, and principal square roots for bounded negative and positive real numbers
Tahmini Süre:2m 30s
Soru 207Soru

At a clothing retailer, the wholesale cost of a leather coat was 50%50\% greater than the wholesale cost of a denim jacket. The following year, the wholesale cost of the leather coat increased by 20%20\%, while the wholesale cost of the denim jacket decreased by 10%10\%. What was the overall percentage increase in the combined wholesale cost of one leather coat and one denim jacket?

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Cevap: 8%8\%

Cevap

An overall increase of 8%8\% in the combined wholesale cost.
Assuming an initial denim jacket cost of 100100, the leather coat costs 150150, giving an initial combined cost of 250250. After a 20%20\% increase, the coat costs 180180, and after a 10%10\% decrease, the jacket costs 9090. The new combined total is 270270. The total increase is 2020, which represents 20250=8%\frac{20}{250} = 8\% of the original combined cost.

Adım Adım Çözüm

1
Define variables for the initial costs of the items.
Let the initial cost of the denim jacket be d=100d = 100. Then the initial cost of the leather coat is 1.50d=1501.50d = 150.
Choosing a convenient base value makes calculating relative percentage changes straightforward.
2
Calculate the initial total cost and the new individual costs after price changes.
Initial total cost = 100+150=250100 + 150 = 250. New cost of leather coat = 150×(1+0.20)=180150 \times (1 + 0.20) = 180. New cost of denim jacket = 100×(10.10)=90100 \times (1 - 0.10) = 90.
Percentage increases and decreases must be applied to their respective starting costs.
3
Compute the new combined total cost and calculate the net percentage change.
New combined total cost = 180+90=270180 + 90 = 270. Dollar change = 270250=20270 - 250 = 20. Net percentage increase = 20250×100%=8%\frac{20}{250} \times 100\% = 8\%.
Percent change is calculated by dividing the absolute change by the original combined base value.

Anahtar Kavram

Combined Percent Change and Weighted Base Values
Soru 208Soru

In Month 1, a data center's two facilities, Facility A and Facility B, consumed a combined total of 120,000 kWh120,000\text{ kWh} of electricity. In Month 2, Facility A decreased its electricity consumption by 15%15\%, while Facility B increased its electricity consumption by 20%20\%. If the combined electricity consumption of the two facilities increased by 6%6\% overall in Month 2, how many kilowatt-hours (kWh\text{kWh}) of electricity did Facility A consume in Month 1?

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Cevap: 48000

Cevap

Facility A consumed 48,000 kWh of electricity in Month 1.
Let AA represent the electricity consumed by Facility A in Month 1. The remaining electricity consumed by Facility B in Month 1 is 120,000A120,000 - A. In Month 2, the decrease in Facility A's consumption is 15%15\% of AA, or 0.15A0.15A, and the increase in Facility B's consumption is 20%20\% of (120,000A)(120,000 - A), or 0.20(120,000A)0.20(120,000 - A). The net increase overall is 6%6\% of 120,000120,000, which is 7,200 kWh7,200\text{ kWh}. Setting up the change equation 0.15A+0.20(120,000A)=7,200-0.15A + 0.20(120,000 - A) = 7,200 leads to 0.35A+24,000=7,200-0.35A + 24,000 = 7,200, which simplifies to 0.35A=16,8000.35A = 16,800. Solving for AA yields A=48,000 kWhA = 48,000\text{ kWh}.

Adım Adım Çözüm

1
Define variables for the initial Month 1 consumption of each facility.
Let AA = Month 1 consumption of Facility A. Month 1 consumption of Facility B = 120,000A120,000 - A.
Expressing one unknown in terms of the total reduces the system to a single variable equation.
2
Determine the net kilowatt-hour change for Month 2.
Net change = 0.06×120,000=7,200 kWh0.06 \times 120,000 = 7,200\text{ kWh}.
An overall increase of 6% applies to the total starting value of 120,000 kWh.
3
Express the individual percentage changes in terms of AA and equate to the net change.
0.15A+0.20(120,000A)=7,200-0.15A + 0.20(120,000 - A) = 7,200.
Facility A's 15% decrease contributes 0.15A-0.15A and Facility B's 20% increase contributes +0.20(120,000A)+0.20(120,000 - A).
4
Solve the linear equation for AA.
0.35A+24,000=7,2000.35A=16,800A=48,000-0.35A + 24,000 = 7,200 \Rightarrow 0.35A = 16,800 \Rightarrow A = 48,000.
Dividing 16,80016,800 by 0.350.35 yields the original consumption of Facility A.

Anahtar Kavram

Weighted Percent Change and Systems of Percent Equations
Soru 209Soru

An automated micro-dispenser delivers liquid reagents in precise doses. Each dose has a volume of 3.6×1053.6 \times 10^{-5} liters. If a reservoir containing 0.01620.0162 liters of reagent is emptied completely by delivering these equal doses, how many doses were delivered?

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Cevap: 450

Cevap

450
Dividing the total volume of 1.62×1021.62 \times 10^{-2} liters by the single dose volume of 3.6×1053.6 \times 10^{-5} liters yields 1.623.6×102(5)=0.45×103=450\frac{1.62}{3.6} \times 10^{-2 - (-5)} = 0.45 \times 10^3 = 450 doses.

Adım Adım Çözüm

1
Express the total reservoir volume in scientific notation
0.0162=1.62×1020.0162 = 1.62 \times 10^{-2} liters
Converting decimals into standard scientific notation simplifies multiplication and division operations.
2
Set up the division for the number of doses
Number of doses=1.62×1023.6×105\text{Number of doses} = \frac{1.62 \times 10^{-2}}{3.6 \times 10^{-5}}
The total volume divided by the volume per single dose yields the total dose count.
3
Compute the division of coefficients and exponent terms independently
1.623.6=0.45\frac{1.62}{3.6} = 0.45 and 102105=102(5)=103\frac{10^{-2}}{10^{-5}} = 10^{-2 - (-5)} = 10^3
Applying the exponent quotient rule 10a/10b=10ab10^a / 10^b = 10^{a-b} yields 2(5)=3-2 - (-5) = 3.
4
Convert from scientific notation to a standard integer
0.45×103=4500.45 \times 10^3 = 450
Multiplying 0.450.45 by 1,0001,000 shifts the decimal point 3 places to the right.

Anahtar Kavram

Division of numbers in scientific notation and place value manipulation
Tahmini Süre:1m 30s
Soru 210Soru

The mass of a sample in a laboratory experiment is given by the expression M=0.000375×10nM = 0.000375 \times 10^n grams, where nn is an integer. When MM is written in standard scientific notation as a×10ka \times 10^k, where 1a<101 \le a < 10 and kk is an integer, the exponent kk is equal to 2-2. What is the value of nn?

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Cevap: 22

Cevap

The value of nn is 22.
Writing 0.0003750.000375 as 3.75×1043.75 \times 10^{-4} allows the mass MM to be rewritten as 3.75×104+n3.75 \times 10^{-4 + n}. Matching this with the standard scientific notation form a×10ka \times 10^k (where a=3.75a = 3.75 and k=2k = -2) gives the equation 4+n=2-4 + n = -2. Solving for nn yields n=2n = 2.

Adım Adım Çözüm

1
Convert the decimal decimal coefficient to scientific notation.
0.000375=3.75×1040.000375 = 3.75 \times 10^{-4}
Moving the decimal point 4 places to the right puts the leading number in the required range 1a<101 \le a < 10.
2
Substitute this conversion back into the expression for MM and combine powers of 10.
M=(3.75×104)×10n=3.75×10n4M = (3.75 \times 10^{-4}) \times 10^n = 3.75 \times 10^{n - 4}
By exponent rules, 10a×10b=10a+b10^a \times 10^b = 10^{a+b}.
3
Equate the exponent of 10 in the simplified expression to the given value of kk.
n4=2    n=2n - 4 = -2 \implies n = 2
The scientific notation requires a×10ka \times 10^k where k=2k = -2, so n4n - 4 must equal 2-2.

Anahtar Kavram

Converting numbers between standard decimal form and scientific notation using place value and exponent properties
Soru 211Soru

What is the smallest positive integer that is a multiple of 18, 24, and 30, and is also a perfect square?

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Cevap: 3600

Cevap

The smallest positive integer that is a multiple of 18, 24, and 30, and is also a perfect square is 3600.
The least common multiple of 18, 24, and 30 is 360, which factors into 2332512^3 \cdot 3^2 \cdot 5^1. For an integer to be a perfect square, all exponents in its prime factorization must be even. Multiplying 360 by 25=102 \cdot 5 = 10 completes the odd exponents to even values (2432522^4 \cdot 3^2 \cdot 5^2), giving 3600, which is the smallest perfect square divisible by 18, 24, and 30.

Adım Adım Çözüm

1
Find the prime factorization of 18, 24, and 30
18=213218 = 2^1 \cdot 3^2, 24=233124 = 2^3 \cdot 3^1, 30=21315130 = 2^1 \cdot 3^1 \cdot 5^1
Decomposing numbers into prime factors allows calculation of the LCM and analysis of perfect square conditions.
2
Calculate the LCM of 18, 24, and 30
LCM(18,24,30)=233251=360\text{LCM}(18, 24, 30) = 2^3 \cdot 3^2 \cdot 5^1 = 360
Any common multiple must be a multiple of the LCM of these three numbers.
3
Determine the smallest factor required to make the prime exponents even
Multiply 360 by 2151=102^1 \cdot 5^1 = 10
A perfect square requires all prime exponents to be even; 2 has power 3 and 5 has power 1 in 360, so one more factor of 2 and one more factor of 5 are required.
4
Compute the final result
360×10=3600360 \times 10 = 3600
3600=243252=6023600 = 2^4 \cdot 3^2 \cdot 5^2 = 60^2, which is a perfect square.

Anahtar Kavram

Prime Factorization, LCM, and Exponent Properties of Perfect Squares
Soru 212Soru

An agricultural cooperative harvested crops from three distinct farming zones: Zone A, Zone B, and Zone C. In Season 1, Zone A accounted for 40%40\% of the cooperative's total crop yield, Zone B accounted for 35%35\%, and Zone C accounted for the remaining 25%25\%.

In Season 2:
- The crop yield in Zone A increased by 15%15\% compared to Season 1.
- The crop yield in Zone B decreased by 20%20\% compared to Season 1.
- The crop yield in Zone C increased by p%p\% compared to Season 1.

If the cooperative's total crop yield in Season 2 was 6%6\% greater than its total crop yield in Season 1, what is the value of pp?

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Cevap: 28

Cevap

The value of pp is 2828.
The correct value of pp is 2828. Calculating the weighted percentage contributions of each zone shows that Zone A contributes a yield equal to 46%46\% of the original total yield and Zone B contributes 28%28\%, making their combined Season 2 contribution 74%74\% of the original total yield. To reach the required total Season 2 yield of 106%106\% of the original total, Zone C must contribute 106%74%=32%106\% - 74\% = 32\% of the original total yield. Since Zone C initially produced 25%25\% of the total yield, the percentage increase for Zone C is 322525×100%=725×100%=28%\frac{32 - 25}{25} \times 100\% = \frac{7}{25} \times 100\% = 28\%.

Adım Adım Çözüm

1
Define total initial yield and express Season 1 yields for each zone in terms of total yield YY.
Zone A yield = 0.40Y0.40Y, Zone B yield = 0.35Y0.35Y, Zone C yield = 0.25Y0.25Y.
Establishing baseline values based on given initial percentage shares.
2
Calculate the Season 2 yields for Zones A and B after their respective percentage changes.
Zone A yield in Season 2 = 0.40Y×1.15=0.46Y0.40Y \times 1.15 = 0.46Y. Zone B yield in Season 2 = 0.35Y×0.80=0.28Y0.35Y \times 0.80 = 0.28Y.
Applying a 15% increase to Zone A and a 20% decrease to Zone B.
3
Set up the total Season 2 yield equation using the given 6% overall increase.
0.46Y+0.28Y+0.25Y(1+p100)=1.06Y0.46Y + 0.28Y + 0.25Y\left(1 + \frac{p}{100}\right) = 1.06Y.
The sum of all three zone yields in Season 2 equals 106% of the total Season 1 yield.
4
Solve for pp.
0.74+0.25(1+p100)=1.06    0.25(1+p100)=0.32    1+p100=1.28    p=280.74 + 0.25\left(1 + \frac{p}{100}\right) = 1.06 \implies 0.25\left(1 + \frac{p}{100}\right) = 0.32 \implies 1 + \frac{p}{100} = 1.28 \implies p = 28.
Subtracting 0.74 from 1.06 gives 0.32, and dividing 0.32 by 0.25 yields 1.28, representing a 28% increase.

Anahtar Kavram

Weighted Percent Change and Base Values
Soru 213Soru

An industrial laboratory prepares a batch of Alloy ZZ weighing 260260 pounds, which consists solely of copper and zinc in a ratio of 7:67 : 6 by weight. A technician then adds 4040 pounds of pure copper to this batch to create Alloy WW. What is the ratio of copper to zinc in Alloy WW?

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Cevap: 3 : 2

Cevap

3 : 2
In Alloy Z, the total weight of 260 pounds is divided into 13 equal parts of 20 pounds each. Thus, copper accounts for 7 parts (140 pounds) and zinc accounts for 6 parts (120 pounds). Adding 40 pounds of pure copper increases the copper content to 180 pounds, while zinc remains at 120 pounds. Comparing copper to zinc yields 180 : 120, which simplifies to 3 : 2.

Adım Adım Çözüm

1
Determine total ratio parts for Alloy Z.
The total number of ratio parts is 7+6=137 + 6 = 13 parts.
To find the weight of each component from a part-to-part ratio, divide the total weight by total ratio parts.
2
Calculate initial weights of copper and zinc in Alloy Z.
Copper weight =260×713=140= 260 \times \frac{7}{13} = 140 pounds; Zinc weight =260×613=120= 260 \times \frac{6}{13} = 120 pounds.
Multiply total weight by each component's fraction of the total.
3
Update component weights after adding pure copper.
New copper weight =140+40=180= 140 + 40 = 180 pounds; Zinc weight remains 120120 pounds.
Only copper is added to the mixture, leaving zinc weight unchanged.
4
Compute and simplify the final ratio of copper to zinc for Alloy W.
Ratio of copper to zinc =180:120=3:2= 180 : 120 = 3 : 2.
Divide both terms by their greatest common divisor, 60.

Anahtar Kavram

Ratios and Component Mixture Adjustment
Soru 214Soru

Let n=2a3bpcn = 2^a \cdot 3^b \cdot p^c, where aa, bb, and cc are positive integers and pp is a prime number strictly greater than 55. The integer nn has exactly 3636 positive divisors, and gcd(n,180)=36\gcd(n, 180) = 36. Which of the following statements MUST be true? Select all such statements.

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Cevap: The integer nn is divisible by 3636.; The exponent cc cannot exceed 33.; The least common multiple of nn and 180180 is equal to 5n5n.

Cevap

The statements asserting that nn is divisible by 3636, that the exponent cc cannot exceed 33, and that lcm(n,180)=5n\text{lcm}(n, 180) = 5n must be true.
The statement that nn is divisible by 3636 is true because a2a \ge 2 and b2b \ge 2. The statement that c3c \le 3 is true because (a+1)(b+1)9(a+1)(b+1) \ge 9, bounding c+14c+1 \le 4. The statement that lcm(n,180)=5n\text{lcm}(n, 180) = 5n is true because max(a,2)=a\max(a, 2) = a, max(b,2)=b\max(b, 2) = b, and 180180 contributes a factor of 515^1.

Adım Adım Çözüm

1
Analyze the GCD condition to establish bounds on exponents aa and bb.
a2a \ge 2 and b2b \ge 2.
Since 180=223251180 = 2^2 \cdot 3^2 \cdot 5^1 and gcd(n,180)=36=2232\gcd(n, 180) = 36 = 2^2 \cdot 3^2, the minimum of the exponents of 22 is 22 (so a2a \ge 2) and the minimum of the exponents of 33 is 22 (so b2b \ge 2).
2
Use the divisor count formula (a+1)(b+1)(c+1)=36(a+1)(b+1)(c+1) = 36 to find constraints on cc.
c3c \le 3.
Since a2    a+13a \ge 2 \implies a+1 \ge 3 and b2    b+13b \ge 2 \implies b+1 \ge 3, the product (a+1)(b+1)9(a+1)(b+1) \ge 9. Therefore, c+1=36(a+1)(b+1)369=4c+1 = \frac{36}{(a+1)(b+1)} \le \frac{36}{9} = 4, which gives c3c \le 3.
3
Evaluate the divisibility of nn by 3636.
nn is divisible by 3636.
Because a2a \ge 2 and b2b \ge 2, 2232=362^2 \cdot 3^2 = 36 divides 2a3bpc=n2^a \cdot 3^b \cdot p^c = n.
4
Calculate lcm(n,180)\text{lcm}(n, 180).
lcm(n,180)=5n\text{lcm}(n, 180) = 5n.
lcm(2a3bpc,223251)=2max(a,2)3max(b,2)51pc=2a3b5pc=5n\text{lcm}(2^a \cdot 3^b \cdot p^c, 2^2 \cdot 3^2 \cdot 5^1) = 2^{\max(a,2)} \cdot 3^{\max(b,2)} \cdot 5^1 \cdot p^c = 2^a \cdot 3^b \cdot 5 \cdot p^c = 5n since a2a \ge 2, b2b \ge 2, and p>5p > 5.
5
Test counterexamples for statement constancy regarding a+b+c=7a+b+c=7 and a=2a=2.
Neither a+b+c=7a+b+c=7 nor a=2a=2 is required.
The choice (a,b,c)=(5,2,1)(a, b, c) = (5, 2, 1) satisfies (5+1)(2+1)(1+1)=36(5+1)(2+1)(1+1) = 36 and gcd(n,180)=36\gcd(n, 180) = 36, yielding a+b+c=87a+b+c=8 \neq 7 and a=52a=5 \neq 2.

Anahtar Kavram

Prime Factorization, Greatest Common Divisor (GCD), and Least Common Multiple (LCM) properties
Soru 215Soru

On the real number line, points PP, QQ, and RR have coordinates xx, yy, and zz, respectively, such that x2=5|x - 2| = 5, y+4=3|y + 4| = 3, and zz is the midpoint of segment PQPQ. If x<yx < y, what is the value of zz?

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Cevap: -2

Cevap

The coordinate of point RR (the value of zz) is 2-2.
Solving the two absolute value equations yields x{3,7}x \in \{-3, 7\} and y{7,1}y \in \{-7, -1\}. Testing the given constraint x<yx < y across all four possible ordered pairs reveals that only x=3x = -3 and y=1y = -1 satisfy the condition, since 3<1-3 < -1 is true while all other pairs fail. The midpoint of points with coordinates 3-3 and 1-1 is 3+(1)2=2\frac{-3 + (-1)}{2} = -2.

Adım Adım Çözüm

1
Solve the absolute value equation x2=5|x - 2| = 5.
x=7x = 7 or x=3x = -3
The equation x2=5|x - 2| = 5 splits into x2=5    x=7x - 2 = 5 \implies x = 7 and x2=5    x=3x - 2 = -5 \implies x = -3.
2
Solve the absolute value equation y+4=3|y + 4| = 3.
y=1y = -1 or y=7y = -7
The equation y+4=3|y + 4| = 3 splits into y+4=3    y=1y + 4 = 3 \implies y = -1 and y+4=3    y=7y + 4 = -3 \implies y = -7.
3
Evaluate all candidate pairs (x,y)(x, y) under the inequality constraint x<yx < y.
The only valid pair is x=3x = -3 and y=1y = -1.
Comparing all four combinations: 7<17 < -1 (false), 7<77 < -7 (false), 3<7-3 < -7 (false), and 3<1-3 < -1 (true).
4
Calculate the midpoint zz of the segment PQPQ.
z=2z = -2
The midpoint of coordinates 3-3 and 1-1 on a number line is given by their average: 3+(1)2=2\frac{-3 + (-1)}{2} = -2.

Anahtar Kavram

Absolute Value Equations and Midpoint on the Real Number Line
Soru 216Soru

If 3x+3x=43^x + 3^{-x} = 4, what is the value of 27x+27x29x+9x+1\frac{27^x + 27^{-x} - 2}{9^x + 9^{-x} + 1}?

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Cevap: 103\frac{10}{3}

Cevap

103\frac{10}{3}
Squaring 3x+3x=43^x + 3^{-x} = 4 yields 9x+2+9x=169^x + 2 + 9^{-x} = 16, which simplifies to 9x+9x=149^x + 9^{-x} = 14. Utilizing the sum of cubes identity gives 27x+27x=(3x+3x)(9x1+9x)=4(141)=5227^x + 27^{-x} = (3^x + 3^{-x})(9^x - 1 + 9^{-x}) = 4(14 - 1) = 52. Substituting these values into the given fraction gives 52214+1=5015=103\frac{52 - 2}{14 + 1} = \frac{50}{15} = \frac{10}{3}.

Adım Adım Çözüm

1
Square the given expression 3x+3x=43^x + 3^{-x} = 4 to determine 9x+9x9^x + 9^{-x}.
(3x+3x)2=9x+2(3x)(3x)+9x=9x+2+9x=16(3^x + 3^{-x})^2 = 9^x + 2(3^x)(3^{-x}) + 9^{-x} = 9^x + 2 + 9^{-x} = 16, which yields 9x+9x=149^x + 9^{-x} = 14.
Expanding the square of a binomial requires accounting for the middle term 23x3x=22 \cdot 3^x \cdot 3^{-x} = 2.
2
Express 27x+27x27^x + 27^{-x} using the sum of cubes factorization identity.
27x+27x=(3x)3+(3x)3=(3x+3x)(9x3x3x+9x)=4(141)=5227^x + 27^{-x} = (3^x)^3 + (3^{-x})^3 = (3^x + 3^{-x})(9^x - 3^x \cdot 3^{-x} + 9^{-x}) = 4(14 - 1) = 52.
The identity a3+b3=(a+b)(a2ab+b2)a^3 + b^3 = (a + b)(a^2 - ab + b^2) allows factoring cubic exponential expressions.
3
Substitute the evaluated terms into the target rational expression and simplify.
\frac{27^x + 27^{-x} - 2}{9^x + 9^{-x} + 1} = \frac{52 - 2}{14 + 1} = \frac{50}{15} = \frac{10}{3}.
Replacing component expressions with their computed values yields the simplified numerical fraction.

Anahtar Kavram

Evaluating high-power exponential expressions using polynomial identity transformations and exponent laws.
Soru 217Soru

Two positive integers xx and yy satisfy x<yx < y, gcd(x,y)=18\gcd(x, y) = 18, and lcm(x,y)=1080\text{lcm}(x, y) = 1080. If xx has exactly 66 positive divisors, what is the value of yy?

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Cevap: 10801080

Cevap

1080
Since gcd(x,y)=18\gcd(x, y) = 18 and lcm(x,y)=1080\text{lcm}(x, y) = 1080, we can express x=18mx = 18m and y=18ny = 18n with gcd(m,n)=1\gcd(m, n) = 1 and m<nm < n. Substituting into lcm(x,y)=18mn=1080\text{lcm}(x, y) = 18mn = 1080 gives mn=60mn = 60. The coprime pairs (m,n)(m, n) with m<nm < n are (1,60)(1, 60), (3,20)(3, 20), (4,15)(4, 15), and (5,12)(5, 12). Testing x=18mx = 18m for each pair: for m=1m = 1, x=18=2132x = 18 = 2^1 \cdot 3^2, which has (1+1)(2+1)=6(1+1)(2+1) = 6 positive divisors. This matches the condition, so n=60n = 60 and y=18×60=1080y = 18 \times 60 = 1080.

Adım Adım Çözüm

1
Express xx and yy in terms of their Greatest Common Divisor
Let x=18mx = 18m and y=18ny = 18n, where mm and nn are positive integers such that m<nm < n and gcd(m,n)=1\gcd(m, n) = 1.
Since gcd(x,y)=18\gcd(x, y) = 18, both numbers must be multiples of 1818, and their remaining factor parts must be coprime.
2
Use the LCM formula lcm(x,y)=18mn\text{lcm}(x, y) = 18mn to find mnmn
18mn=1080    mn=6018mn = 1080 \implies mn = 60.
The least common multiple of 18m18m and 18n18n with gcd(m,n)=1\gcd(m,n)=1 is 18mn18mn.
3
Find all coprime factor pairs (m,n)(m, n) of 6060 with m<nm < n
The prime factorization of 6060 is 2231512^2 \cdot 3^1 \cdot 5^1. Coprime pairs (m,n)(m, n) are (1,60)(1, 60), (3,20)(3, 20), (4,15)(4, 15), and (5,12)(5, 12).
Pairs must be coprime so that gcd(18m,18n)=18\gcd(18m, 18n) = 18 remains true.
4
Determine the number of positive divisors for x=18mx = 18m for each candidate pair
For m=1m = 1, x=18=2132x = 18 = 2^1 \cdot 3^2, which has (1+1)(2+1)=6(1+1)(2+1) = 6 positive divisors.
The number of positive divisors of p1a1p2a2p_1^{a_1} p_2^{a_2} \dots is given by (a1+1)(a2+1)(a_1 + 1)(a_2 + 1) \dots. Only m=1m = 1 gives exactly 66 divisors.
5
Calculate yy
y=18n=1860=1080y = 18n = 18 \cdot 60 = 1080.
Corresponding to m=1m = 1, n=60n = 60 gives y=1080y = 1080.

Anahtar Kavram

Prime Factorization, GCD/LCM Coprime Relationships, and Divisor Counting Formula

Alternatif Yöntem

Alternatively, use gcd(x,y)lcm(x,y)=xy    xy=181080=19440\gcd(x, y) \cdot \text{lcm}(x, y) = x \cdot y \implies x \cdot y = 18 \cdot 1080 = 19440. Since xx has 66 positive divisors and xx is a multiple of 1818, xx must equal 1818 because 18=213218 = 2^1 \cdot 3^2 has (1+1)(2+1)=6(1+1)(2+1) = 6 divisors. Then y=19440/18=1080y = 19440 / 18 = 1080.
Tahmini Süre:1m 30s
Soru 218Soru

In Year 1, a technology firm allocated 40%40\% of its total operating budget to Research and Development (R&D) and the remaining 60%60\% to Business Operations. In Year 2, the amount allocated to R&D was increased by 25%25\% over its Year 1 amount, while the amount allocated to Business Operations was decreased by 15%15\% from its Year 1 amount. If the firm's total operating budget in Year 2 was $505,000\$505,000, what was its total operating budget in Year 1?

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Cevap: $500,000\$500,000

Cevap

The total operating budget in Year 1 was $500,000\$500,000.
The budget allocation in Year 1 assigns 40%40\% to R&D and 60%60\% to Operations. In Year 2, R&D becomes 0.40×1.25=0.500.40 \times 1.25 = 0.50 of the Year 1 budget, and Operations becomes 0.60×0.85=0.510.60 \times 0.85 = 0.51 of the Year 1 budget. Adding these yields a Year 2 total equal to 1.011.01 times the Year 1 budget. Setting 1.01×Year 1 Budget=$505,0001.01 \times \text{Year 1 Budget} = \$505,000 and dividing gives $500,000\$500,000.

Adım Adım Çözüm

1
Define Year 1 components in terms of total Year 1 budget BB.
R&D allocation = 0.40B0.40B; Operations allocation = 0.60B0.60B.
The problem specifies a 40%/60%40\% / 60\% split of the total budget BB in Year 1.
2
Calculate Year 2 allocations after percentage changes.
Year 2 R&D = 0.40B×1.25=0.50B0.40B \times 1.25 = 0.50B; Year 2 Operations = 0.60B×0.85=0.51B0.60B \times 0.85 = 0.51B.
R&D increases by 25%25\% (1+0.25=1.251 + 0.25 = 1.25) and Operations decreases by 15%15\% (10.15=0.851 - 0.15 = 0.85).
3
Sum Year 2 allocations to express total Year 2 budget in terms of BB.
Total Year 2 Budget = 0.50B+0.51B=1.01B0.50B + 0.51B = 1.01B.
Combining both component allocations gives the total budget for Year 2.
4
Solve for the Year 1 budget BB using the given Year 2 total.
1.01B=$505,000    B=505,0001.01=$500,0001.01B = \$505,000 \implies B = \frac{505,000}{1.01} = \$500,000.
Dividing the Year 2 budget by the total growth multiplier yields the original Year 1 budget.

Anahtar Kavram

Weighted Percent Change and Initial Base Calculation
Soru 219Soru

A venture capital fund allocated an initial sum of money between Portfolio Alpha and Portfolio Beta, with Portfolio Alpha receiving 60%60\% of the total sum and Portfolio Beta receiving the remaining 40%40\%. During the first year, the value of Portfolio Alpha increased by 20%20\%, while the value of Portfolio Beta decreased by 15%15\%. During the second year, the value of Portfolio Alpha decreased by 10%10\% relative to its value at the end of the first year, while the value of Portfolio Beta increased by 25%25\% relative to its value at the end of the first year. By what percent did the total combined value of the two portfolios increase from the initial allocation to the end of the second year?

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Cevap: 7.3

Cevap

The total combined value of the two portfolios increased by 7.3%.
To find the net percent change over the two-year period, track each portfolio's value year by year. Assuming an initial combined total of 100,PortfolioAlphabeginsat100, Portfolio Alpha begins at 60 and Portfolio Beta at 40.BytheendofYear1,Alphaincreasesby2040. By the end of Year 1, Alpha increases by 20% to 72 (60×1.2060 \times 1.20), while Beta decreases by 15% to 34(34 ( 40 \times 0.85 ).InYear2,Alphadecreasesby10). In Year 2, Alpha decreases by 10% relative to its Year 1 ending value, becoming 64.80 (72×0.9072 \times 0.90), while Beta increases by 25% relative to its Year 1 ending value, becoming 42.50(42.50 ( 34 \times 1.25 ).ThetotalcombinedvalueattheendofYear2is). The total combined value at the end of Year 2 is 64.80 + 42.50=42.50 = 107.30. Relative to the initial $100 allocation, this represents a net increase of 7.3%.

Adım Adım Çözüm

1
Assign a convenient base value for the initial total investment.
Assume an initial total allocation of 100.PortfolioAlphastartswith100. Portfolio Alpha starts with 60 and Portfolio Beta starts with $40.
Percent changes are proportional and scale-invariant, making $100 a simple base value for calculation.
2
Compute the value of each portfolio at the end of Year 1.
Portfolio Alpha = 60×(1+0.20)=60 \times (1 + 0.20) = 72. Portfolio Beta = 40×(10.15)=40 \times (1 - 0.15) = 34.
Apply Year 1 growth (+20%) and loss (-15%) to their respective starting funds.
3
Compute the value of each portfolio at the end of Year 2.
Portfolio Alpha = 72×(10.10)=72 \times (1 - 0.10) = 64.80. Portfolio Beta = 34×(1+0.25)=34 \times (1 + 0.25) = 42.50.
Apply Year 2 changes (-10% and +25%) to the Year 1 ending values rather than the original principal.
4
Find the final total combined value and calculate the overall net percentage increase.
Combined Year 2 value = 64.80+64.80 + 42.50 = $107.30. Net percentage increase = \frac{107.30 - 100}{100} \times 100\% = 7.3\%.
Compare the final combined sum of 107.30totheinitialcombinedsumof107.30 to the initial combined sum of 100.

Anahtar Kavram

Successive percent changes with shifting base values across multiple assets
Soru 220Soru

If aa, bb, and cc are non-zero integers such that a3b2c<0a^3 b^2 c < 0, a+ba + b is even, and b+cb + c is odd, which of the following expressions MUST be a negative even integer?

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Cevap: ac(b2+1)a c (b^2 + 1)

Cevap

The expression ac(b2+1)a c (b^2 + 1) must be a negative even integer.
The expression ac(b2+1)a c (b^2 + 1) is guaranteed to be negative because ac<0a c < 0 (derived from a3b2c<0a^3 b^2 c < 0) and b2+1>0b^2 + 1 > 0 for all non-zero integers bb. It is guaranteed to be even because aa and cc have opposite parity, meaning one of them must be even, rendering aca c (and thus any integer multiple of aca c) even.

Adım Adım Çözüm

1
Analyze the sign constraint a3b2c<0a^3 b^2 c < 0.
ac<0a c < 0, which means aa and cc have opposite signs.
Since b0b \neq 0, b2b^2 is strictly positive. Dividing a3b2c<0a^3 b^2 c < 0 by b2b^2 yields a3c<0a^3 c < 0. Since a3a^3 has the same sign as aa, ac<0a c < 0.
2
Analyze the parity constraints a+ba + b is even and b+cb + c is odd.
aa and cc have opposite parity (one is even, the other is odd).
If a+ba + b is even, aa and bb share the same parity. If b+cb + c is odd, bb and cc have opposite parity. Substituting the parity of aa for bb shows that aa and cc must have opposite parity.
3
Determine the sign and parity of ac(b2+1)a c (b^2 + 1).
ac(b2+1)a c (b^2 + 1) is strictly negative and even.
Since aa and cc have opposite parity, at least one of them is even, making the product aca c an even integer. Since ac<0a c < 0 and b2+11>0b^2 + 1 \ge 1 > 0, the product of negative aca c and positive (b2+1)(b^2 + 1) is negative and even.

Anahtar Kavram

Combining sign rules (ac<0a c < 0) with even/odd parity logic across multiple variables.
ÖncekiSayfa 11 / 16Sonraki
Arithmetic Alıştırma Soruları — GRE General Test — Sayfa 11 | Examkin