Prime Factorization, GCD, and LCM

28 soru

Soru 1Soru

Let nn be a positive integer whose prime factorization consists only of the prime factors 22 and 33. If nn has exactly 1212 positive divisors and gcd(n,36)=12\gcd(n, 36) = 12, what is the value of nn?

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Cevap: 96

Cevap

The value of nn is 9696.
Representing n=2a×3bn = 2^a \times 3^b, the number of positive divisors is (a+1)(b+1)=12(a+1)(b+1) = 12. The greatest common divisor gcd(n,36)=gcd(2a×3b,22×32)=2min(a,2)×3min(b,2)=12=22×31\gcd(n, 36) = \gcd(2^a \times 3^b, 2^2 \times 3^2) = 2^{\min(a,2)} \times 3^{\min(b,2)} = 12 = 2^2 \times 3^1. This requires min(a,2)=2    a2\min(a,2) = 2 \implies a \ge 2 and min(b,2)=1    b=1\min(b,2) = 1 \implies b = 1. Substituting b=1b = 1 into (a+1)(1+1)=12(a+1)(1+1) = 12 gives 2(a+1)=122(a+1) = 12, so a=5a = 5. Therefore, n=25×31=32×3=96n = 2^5 \times 3^1 = 32 \times 3 = 96.

Adım Adım Çözüm

1
Set up the prime factorization of nn and the divisor count equation.
n=2a×3bn = 2^a \times 3^b and (a+1)(b+1)=12(a + 1)(b + 1) = 12.
Since the prime factors of nn are only 22 and 33, nn must take the form 2a×3b2^a \times 3^b, where the number of positive divisors is (a+1)(b+1)(a+1)(b+1).
2
Analyze the exponent requirements using the greatest common divisor.
a2a \ge 2 and b=1b = 1.
gcd(2a×3b,22×32)=2min(a,2)×3min(b,2)=22×31\gcd(2^a \times 3^b, 2^2 \times 3^2) = 2^{\min(a,2)} \times 3^{\min(b,2)} = 2^2 \times 3^1. Matching powers gives min(a,2)=2    a2\min(a,2) = 2 \implies a \ge 2, and min(b,2)=1    b=1\min(b,2) = 1 \implies b = 1.
3
Solve for exponent aa and calculate nn.
a=5a = 5, giving n=25×31=96n = 2^5 \times 3^1 = 96.
Substituting b=1b = 1 into (a+1)(1+1)=12(a+1)(1+1) = 12 gives 2(a+1)=12    a=52(a+1) = 12 \implies a = 5, which satisfies a2a \ge 2.

Anahtar Kavram

Prime exponent rules for GCD and divisor counting
Tahmini Süre:2m 0s
Soru 2Soru

Let K=25×34×53×112K = 2^5 \times 3^4 \times 5^3 \times 11^2. How many positive integer factors of KK are divisible by 300300 but are not divisible by 900900?

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Cevap: 24

Cevap

24
The correct answer 24 is obtained by analyzing the prime factorizations 300=22×31×52300 = 2^2 \times 3^1 \times 5^2 and 900=22×32×52900 = 2^2 \times 3^2 \times 5^2. Any factor f=2a×3b×5c×11df = 2^a \times 3^b \times 5^c \times 11^d must satisfy a{2,3,4,5}a \in \{2, 3, 4, 5\} (4 choices), b=1b = 1 (1 choice, since b1b \ge 1 for 300 but b<2b < 2 for 900), c{2,3}c \in \{2, 3\} (2 choices), and d{0,1,2}d \in \{0, 1, 2\} (3 choices). Multiplying these choices gives 4×1×2×3=244 \times 1 \times 2 \times 3 = 24.

Adım Adım Çözüm

1
Express any factor of KK in terms of prime factor exponent constraints.
Any factor ff of KK has the form f=2a×3b×5c×11df = 2^a \times 3^b \times 5^c \times 11^d, where 0a50 \le a \le 5, 0b40 \le b \le 4, 0c30 \le c \le 3, and 0d20 \le d \le 2.
The prime factors of ff must be subsets of the prime factors of KK with exponents not exceeding those in KK.
2
Find the prime factorizations of 300300 and 900900.
300=22×31×52300 = 2^2 \times 3^1 \times 5^2 and 900=22×32×52900 = 2^2 \times 3^2 \times 5^2.
Divisibility criteria correspond to minimum exponent requirements for each prime factor.
3
Apply the divisibility conditions to determine constraints on each exponent.
For ff to be divisible by 300300, we need a2a \ge 2, b1b \ge 1, and c2c \ge 2. For ff to NOT be divisible by 900900, we must have b<2b < 2. Thus, b=1b = 1.
Combining b1b \ge 1 and b<2b < 2 uniquely restricts bb to 11.
4
Count the number of valid choices for each exponent.
a{2,3,4,5}a \in \{2, 3, 4, 5\} (44 choices), b{1}b \in \{1\} (11 choice), c{2,3}c \in \{2, 3\} (22 choices), and d{0,1,2}d \in \{0, 1, 2\} (33 choices).
The exponent dd is unrestricted by 300300 or 900900, so it can take any valid power present in KK.
5
Multiply the number of independent choices using the fundamental counting principle.
4×1×2×3=244 \times 1 \times 2 \times 3 = 24.
Each exponent choice can be paired independently to form a unique factor.

Anahtar Kavram

Counting Divisors Using Prime Exponent Constraints
Soru 3Soru

Let xx and yy be positive integers such that gcd(x,y)=14\gcd(x, y) = 14 and lcm(x,y)=420\text{lcm}(x, y) = 420. Which of the following values could be the sum x+yx + y? Select all such values.

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Cevap: 154; 182; 238

Cevap

The possible values for the sum x+yx + y are 154, 182, and 238.
By writing x=14ax = 14a and y=14by = 14b with gcd(a,b)=1\gcd(a, b) = 1, the relation lcm(x,y)=14ab=420\text{lcm}(x, y) = 14ab = 420 requires ab=30ab = 30. The positive coprime factor pairs of 30 are (1,30)(1, 30), (2,15)(2, 15), (3,10)(3, 10), and (5,6)(5, 6). Multiplying these pairs by 14 gives the possible sums 434, 238, 182, and 154. Therefore, the options equal to 154, 182, and 238 are all correct.

Adım Adım Çözüm

1
Express xx and yy in terms of their greatest common divisor.
Let x=14ax = 14a and y=14by = 14b, where aa and bb are positive integers such that gcd(a,b)=1\gcd(a, b) = 1.
Factoring out the greatest common divisor leaves coprime quotient factors aa and bb.
2
Relate the least common multiple to aa and bb.
\text{lcm}(x, y) = 14ab = 420 \implies ab = \frac{420}{14} = 30$.
The least common multiple of two numbers sharing a GCD of gg is given by gabg \cdot a \cdot b.
3
Find all coprime pairs (a,b)(a, b) with aba \le b whose product is 30.
The prime factorization of 30 is 2×3×52 \times 3 \times 5. The valid coprime pairs (a,b)(a, b) are (1,30)(1, 30), (2,15)(2, 15), (3,10)(3, 10), and (5,6)(5, 6).
Since gcd(a,b)=1\gcd(a, b) = 1, all factors of 30 split into pairs of coprime integers.
4
Calculate the corresponding values of xx, yy, and their sum x+yx + y for each pair.
Pair (1, 30): x=14,y=420    x+y=434x = 14, y = 420 \implies x + y = 434.
Pair (2, 15): x=28,y=210    x+y=238x = 28, y = 210 \implies x + y = 238.
Pair (3, 10): x=42,y=140    x+y=182x = 42, y = 140 \implies x + y = 182.
Pair (5, 6): x=70,y=84    x+y=154x = 70, y = 84 \implies x + y = 154.
Multiplying each pair by the GCD of 14 yields the original integers xx and yy.

Anahtar Kavram

Relationship between GCD, LCM, and prime factorization of quotient factors
Soru 4Soru

A positive integer nn has the prime factorization n=2a3b5cn = 2^a \cdot 3^b \cdot 5^c, where aa, bb, and cc are positive integers. If nn is divisible by 3636 and is a divisor of 54005{}400, which of the following values could be the total number of positive divisors of nn? Select all such values.

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Cevap: 18; 27; 32

Cevap

18, 27, and 32 are all possible total numbers of positive divisors for nn.
Prime factorization gives 36=223236 = 2^2 \cdot 3^2 and 5400=2333525{}400 = 2^3 \cdot 3^3 \cdot 5^2. For n=2a3b5cn = 2^a \cdot 3^b \cdot 5^c to be a multiple of 36 and a divisor of 5,400 with positive integer exponents, a{2,3}a \in \{2,3\}, b{2,3}b \in \{2,3\}, and c{1,2}c \in \{1,2\}. The total number of divisors is (a+1)(b+1)(c+1)(a+1)(b+1)(c+1). The possible values for this product are 18, 24, 27, 32, 36, and 48. Among the choices, 18, 27, and 32 are valid values.

Adım Adım Çözüm

1
Find the prime factorizations of the boundary numbers 36 and 5,400.
36=223236 = 2^2 \cdot 3^2 and 5400=2333525{}400 = 2^3 \cdot 3^3 \cdot 5^2.
Establishing the prime factor bounds determines the range of possible values for exponents aa, bb, and cc.
2
Determine the constraints on exponents aa, bb, and cc.
Since 36n36 \mid n, a2a \ge 2, b2b \ge 2, and c1c \ge 1 (given cc is a positive integer). Since n5400n \mid 5{}400, a3a \le 3, b3b \le 3, and c2c \le 2. Thus, a{2,3}a \in \{2, 3\}, b{2,3}b \in \{2, 3\}, and c{1,2}c \in \{1, 2\}.
Divisibility rules require prime factor exponents of a multiple to be greater than or equal to those of the divisor, and exponents of a divisor to be less than or equal to those of the multiple.
3
Calculate all possible total divisor counts using the formula d(n)=(a+1)(b+1)(c+1)d(n) = (a+1)(b+1)(c+1).
Possible factor values are (a+1){3,4}(a+1) \in \{3, 4\}, (b+1){3,4}(b+1) \in \{3, 4\}, and (c+1){2,3}(c+1) \in \{2, 3\}. Evaluating all combinations yields: 332=183 \cdot 3 \cdot 2 = 18, 333=273 \cdot 3 \cdot 3 = 27, 342=243 \cdot 4 \cdot 2 = 24, 343=363 \cdot 4 \cdot 3 = 36, 442=324 \cdot 4 \cdot 2 = 32, and 443=484 \cdot 4 \cdot 3 = 48.
The total number of positive integer divisors is found by adding 1 to each exponent in the prime factorization and multiplying the results.
4
Compare the calculated divisor counts with the options provided.
The values 18, 27, and 32 appear in the calculated set of possible total divisors.
Direct matching identifies all valid options.

Anahtar Kavram

Prime factor exponent bounds and total number of positive divisors formula
Soru 5Soru

Two positive integers mm and nn satisfy gcd(m,n)=20\gcd(m, n) = 20 and lcm(m,n)=4200\text{lcm}(m, n) = 4{}200. It is given that mm is divisible by 77 and has exactly 2424 positive integer divisors. If nn is a multiple of 33, what is the value of nn?

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Cevap: 6060

Cevap

The value of nn is 6060.
Prime factorization reveals that gcd(m,n)=22305170\gcd(m,n) = 2^2 \cdot 3^0 \cdot 5^1 \cdot 7^0 and lcm(m,n)=23315271\text{lcm}(m,n) = 2^3 \cdot 3^1 \cdot 5^2 \cdot 7^1. The condition that nn is a multiple of 33 fixes the exponent of 33 in nn to 11 (so mm has exponent 00). The condition that mm is a multiple of 77 fixes the exponent of 77 in mm to 11 (so nn has exponent 00). For m=2a305c71m = 2^a \cdot 3^0 \cdot 5^c \cdot 7^1, its divisor count equation 2(a+1)(c+1)=242(a+1)(c+1) = 24 simplifies to (a+1)(c+1)=12(a+1)(c+1) = 12. Since a{2,3}a \in \{2, 3\} and c{1,2}c \in \{1, 2\}, the only valid solution is a=3a=3 and c=2c=2. This leaves nn with exponents 22 for prime 22, 11 for prime 33, 11 for prime 55, and 00 for prime 77, giving n=22315170=60n = 2^2 \cdot 3^1 \cdot 5^1 \cdot 7^0 = 60.

Adım Adım Çözüm

1
Express the GCD and LCM in prime factorized form.
gcd(m,n)=20=22305170\gcd(m, n) = 20 = 2^2 \cdot 3^0 \cdot 5^1 \cdot 7^0 and lcm(m,n)=4200=23315271\text{lcm}(m, n) = 4{}200 = 2^3 \cdot 3^1 \cdot 5^2 \cdot 7^1.
The prime factor exponents of mm and nn must have minimums equal to the GCD exponents and maximums equal to the LCM exponents.
2
Determine the exponents of prime factors 33 and 77 for mm and nn.
Since nn is divisible by 33, exponent of 33 in nn is 11, so exponent of 33 in mm is 00. Since mm is divisible by 77, exponent of 77 in mm is 11, so exponent of 77 in nn is 00.
Each prime exponent in lcm(m,n)\text{lcm}(m, n) must belong to at least one of the numbers.
3
Use the divisor count of mm to find its remaining exponents for primes 22 and 55.
Let m=2a305c71m = 2^a \cdot 3^0 \cdot 5^c \cdot 7^1, where a{2,3}a \in \{2, 3\} and c{1,2}c \in \{1, 2\}. The number of positive divisors is (a+1)(0+1)(c+1)(1+1)=2(a+1)(c+1)=24(a+1)(0+1)(c+1)(1+1) = 2(a+1)(c+1) = 24, giving (a+1)(c+1)=12(a+1)(c+1) = 12. Testing a=2    c=3a=2 \implies c=3 (invalid range). Testing a=3    c=2a=3 \implies c=2 (valid). Thus m=23305271=1400m = 2^3 \cdot 3^0 \cdot 5^2 \cdot 7^1 = 1{}400.
The total number of positive integer divisors of p1e1p2e2p_1^{e_1} p_2^{e_2} \cdots is given by (e1+1)(e2+1)(e_1+1)(e_2+1)\cdots.
4
Determine the prime exponents for nn and calculate its value.
Since a=3a=3, nn gets 222^2. Since c=2c=2, nn gets 515^1. Together with 313^1 and 707^0, n=22315170=60n = 2^2 \cdot 3^1 \cdot 5^1 \cdot 7^0 = 60.
For each prime pp, the exponent in nn must match the bound opposite to mm to satisfy both gcd\gcd and lcm\text{lcm}.

Anahtar Kavram

Prime exponent analysis of GCD and LCM alongside the divisor count formula
Soru 6Soru

Two automated timers are set to chime at regular intervals. The first timer chimes every 1212 minutes, and the second timer chimes every 1818 minutes. If both timers chime simultaneously at 12:00 PM, how many minutes will pass before they next chime at the exact same time?

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Cevap: 36

Cevap

36 minutes
The time interval between simultaneous chimes is given by the least common multiple (LCM) of the two individual intervals, 1212 minutes and 1818 minutes. Using prime factorization, 12=22×312 = 2^2 \times 3 and 18=2×3218 = 2 \times 3^2. The LCM takes the highest power of each prime present: 22×32=4×9=362^2 \times 3^2 = 4 \times 9 = 36. Thus, 3636 minutes will elapse before the timers chime together again.

Adım Adım Çözüm

1
Find the prime factorizations of 12 and 18
12=22×312 = 2^2 \times 3 and 18=2×3218 = 2 \times 3^2
Expressing numbers as products of prime factors allows us to easily compute the least common multiple.
2
Calculate the Least Common Multiple (LCM)
LCM(12,18)=2max(2,1)×3max(1,2)=22×32=36\text{LCM}(12, 18) = 2^{\max(2,1)} \times 3^{\max(1,2)} = 2^2 \times 3^2 = 36
The next simultaneous occurrence of periodic events is given by the LCM of their periods.

Anahtar Kavram

Least Common Multiple (LCM) of periodic events
Soru 7Soru

Two positive integers xx and yy have a greatest common divisor (GCD) of 66 and a least common multiple (LCM) of 108108. If x=18x = 18, what is the value of yy?

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Cevap: 3636

Cevap

The value of yy is 3636.
For any two positive integers xx and yy, their product equals the product of their greatest common divisor and least common multiple: xy=GCD(x,y)LCM(x,y)x \cdot y = \text{GCD}(x,y) \cdot \text{LCM}(x,y). Substituting x=18x = 18, GCD=6\text{GCD} = 6, and LCM=108\text{LCM} = 108 gives 18y=6108=64818y = 6 \cdot 108 = 648. Dividing both sides by 1818 yields y=36y = 36.

Adım Adım Çözüm

1
State the fundamental identity relating GCD, LCM, and two positive integers.
x×y=GCD(x,y)×LCM(x,y)x \times y = \text{GCD}(x,y) \times \text{LCM}(x,y)
For any two positive integers, the product of the numbers is equal to the product of their greatest common divisor and least common multiple.
2
Substitute the known values x=18x = 18, GCD=6\text{GCD} = 6, and LCM=108\text{LCM} = 108 into the equation.
18×y=6×10818 \times y = 6 \times 108
Replace the abstract variables with the specific values provided in the question stem.
3
Multiply the numbers on the right side of the equation.
18×y=64818 \times y = 648
Simplify the product of the GCD and LCM.
4
Divide both sides by 1818 to isolate yy.
y=64818=36y = \frac{648}{18} = 36
Solve for the unknown integer yy.

Anahtar Kavram

Relationship between GCD, LCM, and the product of two positive integers
Tahmini Süre:1m 0s
Soru 8Soru

Which of the following statements about the positive integer 180180 are true? Select all that apply.

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Cevap: The number of distinct prime factors of 180180 is 33.; The greatest common divisor (GCD) of 180180 and 7575 is 1515.

Cevap

The true statements are that 180180 has 33 distinct prime factors and that the greatest common divisor of 180180 and 7575 is 1515.
The prime factorization of 180180 is 22×32×512^2 \times 3^2 \times 5^1, showing exactly 33 distinct prime factors (2,3,52, 3, 5). Additionally, comparing this with 75=31×5275 = 3^1 \times 5^2 confirms that their greatest common divisor is 31×51=153^1 \times 5^1 = 15.

Adım Adım Çözüm

1
Find the prime factorization of 180180.
180=22×32×51180 = 2^2 \times 3^2 \times 5^1.
Decomposing 180180 into prime factors provides the foundation to evaluate statements regarding prime factors, GCD, and LCM.
2
Count the distinct prime factors of 180180.
The distinct prime bases are 22, 33, and 55, giving 33 distinct prime factors.
Exponents represent multiplicity, so counting distinct bases yields the number of distinct prime factors.
3
Calculate the GCD of 180180 and 7575.
Since 75=31×5275 = 3^1 \times 5^2, GCD(180,75)=3min(2,1)×5min(1,2)=31×51=15\text{GCD}(180, 75) = 3^{\min(2,1)} \times 5^{\min(1,2)} = 3^1 \times 5^1 = 15.
The GCD is found by taking the minimum exponent for each shared prime factor.
4
Verify definition of prime numbers and divisibility rules for remaining choices.
11 is not prime (smallest prime factor is 22), and LCM(180,30)=180\text{LCM}(180, 30) = 180 because 3030 is a factor of 180180.
Eliminate false statements based on arithmetic definitions and divisibility properties.

Anahtar Kavram

Prime Factorization, Greatest Common Divisor (GCD), and Least Common Multiple (LCM)
Soru 9Soru

What is the sum of all distinct prime factors of 420420?

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Cevap: 1717

Cevap

The sum of all distinct prime factors of 420420 is 1717.
The prime factorization of 420420 is 22×3×5×72^2 \times 3 \times 5 \times 7. The distinct prime numbers in this factorization are 22, 33, 55, and 77. Adding these values together yields 2+3+5+7=172 + 3 + 5 + 7 = 17.

Adım Adım Çözüm

1
Find the prime factorization of 420420.
420=22×3×5×7420 = 2^2 \times 3 \times 5 \times 7
Decompose 420420 into prime components: 420=10×42=(2×5)×(2×3×7)=22×3×5×7420 = 10 \times 42 = (2 \times 5) \times (2 \times 3 \times 7) = 2^2 \times 3 \times 5 \times 7.
2
Identify the set of distinct prime factors.
The distinct prime factors are 2,3,5,2, 3, 5, and 77.
Exponents are ignored when selecting unique prime factors.
3
Calculate the sum of the distinct prime factors.
2+3+5+7=172 + 3 + 5 + 7 = 17
Add the unique prime factors together.

Anahtar Kavram

Prime Factorization
Tahmini Süre:45s
Soru 10Soru

Two positive integers aa and bb have prime factorizations of the form a=2x×3y×5za = 2^x \times 3^y \times 5^z and b=2u×3v×5wb = 2^u \times 3^v \times 5^w, where x,y,z,u,v,wx, y, z, u, v, w are non-negative integers. The greatest common divisor (GCD) of aa and bb is 180180, and the least common multiple (LCM) of aa and bb is 54,00054,000. If aa has exactly 2424 positive divisors, what is the value of bb?

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Cevap: 18000

Cevap

18000
Prime factorizing GCD(a,b)=180=22×32×51\text{GCD}(a,b) = 180 = 2^2 \times 3^2 \times 5^1 and LCM(a,b)=54,000=24×33×53\text{LCM}(a,b) = 54,000 = 2^4 \times 3^3 \times 5^3 reveals that the pair of exponents for bases 2,3,52, 3, 5 are {2,4}\{2, 4\}, {2,3}\{2, 3\}, and {1,3}\{1, 3\} respectively. Applying the total divisor formula (x+1)(y+1)(z+1)=24(x+1)(y+1)(z+1) = 24 for aa, x+1x+1 must divide 2424. Since x{2,4}x \in \{2, 4\}, xx must be 22 (since 55 does not divide 2424). This leaves (y+1)(z+1)=8(y+1)(z+1) = 8. With y{2,3}y \in \{2, 3\}, y+1y+1 must be 44 (since 33 does not divide 88), giving y=3y = 3 and z=1z = 1. Thus, a=22×33×51a = 2^2 \times 3^3 \times 5^1. The remaining exponent choices for bb are u=4u = 4, v=2v = 2, and w=3w = 3, giving b=24×32×53=18,000b = 2^4 \times 3^2 \times 5^3 = 18,000.

Adım Adım Çözüm

1
Factorize GCD and LCM into prime bases.
GCD = 2^2 * 3^2 * 5^1; LCM = 2^4 * 3^3 * 5^3.
GCD represents the minimum prime exponents and LCM represents the maximum prime exponents of a and b.
2
Set up candidate exponent pairs for primes 2, 3, and 5.
{x, u} = {2, 4}, {y, v} = {2, 3}, and {z, w} = {1, 3}.
For any prime p, min(exp_p(a), exp_p(b)) = exp_p(GCD) and max(exp_p(a), exp_p(b)) = exp_p(LCM).
3
Solve for x, y, and z using the divisor count formula d(a) = (x+1)(y+1)(z+1) = 24.
x = 2, y = 3, z = 1.
If x = 4, then x+1 = 5, which is not a factor of 24. Thus x = 2. Then (y+1)(z+1) = 8. Since y in {2, 3}, y+1 = 4 implies y = 3 and z = 1.
4
Determine the exponents of b and calculate b.
u = 4, v = 2, w = 3, so b = 2^4 * 3^2 * 5^3 = 18,000.
Complementary values from the sets {x,u}, {y,v}, and {z,w} give the exponents for b.

Anahtar Kavram

Relationship between prime factor exponents in GCD, LCM, and divisor counting functions.
Soru 11Soru

Let mm and nn be positive integers whose prime factorizations consist only of the prime factors 22, 33, and 55. The greatest common divisor of mm and nn is 360360, and their least common multiple is 108,000108,000. If the power of 22 in the prime factorization of mm is strictly greater than the power of 22 in the prime factorization of nn, and mm has exactly 3636 positive divisors, what is the total number of positive divisors of nn?

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Cevap: 6464

Cevap

The total number of positive divisors of nn is 6464.
By writing the GCD and LCM in prime factorized form, GCD(m,n)=23×32×51\text{GCD}(m,n) = 2^3 \times 3^2 \times 5^1 and LCM(m,n)=25×33×53\text{LCM}(m,n) = 2^5 \times 3^3 \times 5^3. Given a>xa > x for the exponent of 22, we obtain a=5a=5 and x=3x=3. Using the divisor count formula for mm, 6(b+1)(c+1)=366(b+1)(c+1) = 36, which requires (b+1)(c+1)=6(b+1)(c+1) = 6. Testing possible exponent values b{2,3}b \in \{2,3\} reveals that only b=2b=2 yields an integer exponent c=1c=1. This uniquely determines n=23×33×53n = 2^3 \times 3^3 \times 5^3. Calculating (3+1)(3+1)(3+1)(3+1)(3+1)(3+1) gives 6464 positive divisors.

Adım Adım Çözüm

1
Express the greatest common divisor (GCD) and least common multiple (LCM) in prime factorization form.
GCD(m,n)=360=23×32×51\text{GCD}(m, n) = 360 = 2^3 \times 3^2 \times 5^1 and LCM(m,n)=108,000=25×33×53\text{LCM}(m, n) = 108,000 = 2^5 \times 3^3 \times 5^3.
Prime factorizations allow direct comparison of the minimum and maximum exponents for each prime factor.
2
Determine the exponent of 22 for both integers.
For prime factor 22, min(a,x)=3\min(a, x) = 3 and max(a,x)=5\max(a, x) = 5. Since the exponent of 22 in mm is strictly greater than in nn (a>xa > x), a=5a = 5 and x=3x = 3.
The GCD gives the lower exponent bound while the LCM gives the upper exponent bound.
3
Use the number of divisors of mm to solve for its remaining exponents.
Let m=25×3b×5cm = 2^5 \times 3^b \times 5^c. The number of positive divisors of mm is (5+1)(b+1)(c+1)=6(b+1)(c+1)=36(5+1)(b+1)(c+1) = 6(b+1)(c+1) = 36, so (b+1)(c+1)=6(b+1)(c+1) = 6. Since b{2,3}b \in \{2, 3\}, if b=3b = 3 then b+1=4b+1=4 which does not divide 66. Thus, b=2b = 2 and c=1c = 1.
The divisor count formula requires integer exponents, uniquely identifying b=2b = 2 and c=1c = 1 for mm.
4
Determine the exponents for nn and calculate its divisor count.
Since b=2b = 2 and max(b,y)=3\max(b, y) = 3, y=3y = 3. Since c=1c = 1 and max(c,z)=3\max(c, z) = 3, z=3z = 3. Thus n=23×33×53n = 2^3 \times 3^3 \times 5^3, and its divisor count is (3+1)(3+1)(3+1)=64(3+1)(3+1)(3+1) = 64.
Combining the max/min constraints from LCM/GCD yields all exponents of nn.

Anahtar Kavram

GCD and LCM Prime Exponent Relations & Divisor Counting Formula
Tahmini Süre:3m 0s
Soru 12Soru

Let aa and bb be positive integers such that gcd(a,b)=60\gcd(a, b) = 60 and lcm(a,b)=75,600\text{lcm}(a, b) = 75,600. Which of the following statements must be true? Select all that apply.

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Cevap: The product abab is equal to 4,536,0004,536,000.; Neither aa nor bb can be divisible by 4949.; There are exactly 88 distinct unordered pairs of positive integers {a,b}\{a, b\} that satisfy the given conditions.

Cevap

The statements asserting that ab=4,536,000ab = 4,536,000, that neither number is divisible by 4949, and that there are exactly 88 distinct unordered pairs {a,b}\{a, b\} are all correct.
The product of the GCD and LCM of two numbers always yields their product, confirming ab=4,536,000ab = 4,536,000. The prime factorization of the LCM shows that 77 appears only to the first power, making divisibility by 4949 impossible for either number. Finally, assigning the minimum and maximum prime exponents across the four distinct prime factors (2,3,5,7)(2, 3, 5, 7) yields 24=162^4 = 16 ordered pairs, which corresponds to exactly 88 unordered pairs.

Adım Adım Çözüm

1
Apply the product identity for GCD and LCM.
ab=gcd(a,b)×lcm(a,b)=60×75,600=4,536,000ab = \gcd(a, b) \times \text{lcm}(a, b) = 60 \times 75,600 = 4,536,000.
The product of two positive integers is always equal to the product of their greatest common divisor and least common multiple.
2
Find the prime factorizations of gcd(a,b)\gcd(a, b) and lcm(a,b)\text{lcm}(a, b) to determine exponent bounds.
gcd(a,b)=22×31×51×70\gcd(a, b) = 2^2 \times 3^1 \times 5^1 \times 7^0 and lcm(a,b)=24×33×52×71\text{lcm}(a, b) = 2^4 \times 3^3 \times 5^2 \times 7^1.
The exponent of each prime factor in gcd(a,b)\gcd(a, b) gives the minimum exponent in aa and bb, while the exponent in lcm(a,b)\text{lcm}(a, b) gives the maximum exponent.
3
Evaluate prime factor constraints for prime 77 and prime 33.
Maximum power of 77 in aa or bb is 71=77^1 = 7, so neither can be divisible by 4949. For prime 33, one integer has 313^1 (not divisible by 99) and the other has 33=273^3 = 27.
An integer is divisible by 49=7249 = 7^2 only if its prime factorization contains 727^2 or higher. Similarly, a number is a multiple of 9=329 = 3^2 only if its prime exponent for 33 is at least 22.
4
Calculate the total number of distinct unordered pairs {a,b}\{a, b\}.
For each of the 44 prime factors (2,3,5,72, 3, 5, 7), there are 22 choices for which integer gets the higher exponent. Total ordered pairs (a,b)=24=16(a, b) = 2^4 = 16. Unordered pairs {a,b}=16/2=8\{a, b\} = 16 / 2 = 8.
Since min<max\min < \max for all prime factors, aba \neq b for all pairs, allowing exact division by 22 to account for symmetry.
5
Analyze gcd(a+b,60)\gcd(a + b, 60).
Since 60a60 \mid a and 60b60 \mid b, it follows that 60(a+b)60 \mid (a + b), making gcd(a+b,60)=60\gcd(a + b, 60) = 60.
If a number kk divides both aa and bb, it must divide their linear combination a+ba + b.

Anahtar Kavram

Prime Factorization, GCD-LCM Identities, and Counting Valid Integer Pairs
Soru 13Soru

A positive integer nn has a prime factorization of the form 2x×3y×7z2^x \times 3^y \times 7^z, where xx, yy, and zz are positive integers. The greatest common divisor of nn and 420420 is 8484, and the least common multiple of nn and 420420 is 8,8208,820. What is the total number of positive integer factors of nn?

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Cevap: 2727

Cevap

The total number of positive integer factors of nn is 2727.
By prime factorizing 420420, 8484, and 8,8208,820, we find that 420=22×31×51×71420 = 2^2 \times 3^1 \times 5^1 \times 7^1, gcd(n,420)=22×31×71\gcd(n, 420) = 2^2 \times 3^1 \times 7^1, and lcm(n,420)=22×32×51×72\text{lcm}(n, 420) = 2^2 \times 3^2 \times 5^1 \times 7^2. Comparing the minimum and maximum powers for each prime factor shows that n=22×32×72n = 2^2 \times 3^2 \times 7^2. Applying the divisor counting formula gives (2+1)(2+1)(2+1)=27(2+1)(2+1)(2+1) = 27.

Adım Adım Çözüm

1
Express all given values in their prime factorized forms.
420=22×31×51×71420 = 2^2 \times 3^1 \times 5^1 \times 7^1, gcd(n,420)=84=22×31×71\gcd(n, 420) = 84 = 2^2 \times 3^1 \times 7^1, and lcm(n,420)=8,820=22×32×51×72\text{lcm}(n, 420) = 8,820 = 2^2 \times 3^2 \times 5^1 \times 7^2.
Finding the prime factorizations allows comparison of prime exponent bounds for GCD and LCM.
2
Determine the exponents xx, yy, and zz for n=2x×3y×7zn = 2^x \times 3^y \times 7^z.
For prime 22: max(x,2)=2\max(x, 2) = 2 and min(x,2)=2    x=2\min(x, 2) = 2 \implies x = 2.
For prime 33: max(y,1)=2\max(y, 1) = 2 and min(y,1)=1    y=2\min(y, 1) = 1 \implies y = 2.
For prime 77: max(z,1)=2\max(z, 1) = 2 and min(z,1)=1    z=2\min(z, 1) = 1 \implies z = 2.
GCD takes the minimum exponent of each prime factor, while LCM takes the maximum exponent.
3
Calculate the total number of positive factors of n=22×32×72n = 2^2 \times 3^2 \times 7^2.
Total factors =(x+1)(y+1)(z+1)=(2+1)(2+1)(2+1)=3×3×3=27= (x + 1)(y + 1)(z + 1) = (2 + 1)(2 + 1)(2 + 1) = 3 \times 3 \times 3 = 27.
The number of positive divisors of p1ap2bpkkp_1^{a} p_2^{b} \dots p_k^{k} is (a+1)(b+1)(k+1)(a+1)(b+1)\dots(k+1).

Anahtar Kavram

Relationship between prime factorization, greatest common divisor (GCD), least common multiple (LCM), and the number of positive divisors.
Soru 14Soru

A positive integer nn has the prime factorization 2a3b5c2^a \cdot 3^b \cdot 5^c, where aa, bb, and cc are positive integers. Given that gcd(n,7200)=360\gcd(n, 7{}200) = 360 and lcm(n,1080)=3240\text{lcm}(n, 1{}080) = 3{}240, what is the value of a+b+ca + b + c?

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Cevap: 8

Cevap

8
By prime factorizing each given term, 7200=2532527{}200 = 2^5 \cdot 3^2 \cdot 5^2, 360=233251360 = 2^3 \cdot 3^2 \cdot 5^1, 1080=2333511{}080 = 2^3 \cdot 3^3 \cdot 5^1, and 3240=2334513{}240 = 2^3 \cdot 3^4 \cdot 5^1. Applying the definition of GCD as taking the minimum exponent gives min(a,5)=3    a=3\min(a, 5) = 3 \implies a = 3 and min(c,2)=1    c=1\min(c, 2) = 1 \implies c = 1. Applying the definition of LCM as taking the maximum exponent gives max(b,3)=4    b=4\max(b, 3) = 4 \implies b = 4. Thus, a+b+c=3+4+1=8a + b + c = 3 + 4 + 1 = 8.

Adım Adım Çözüm

1
Find the prime factorizations of the given integers and the GCD/LCM values.
7200=2532527{}200 = 2^5 \cdot 3^2 \cdot 5^2, 360=233251360 = 2^3 \cdot 3^2 \cdot 5^1, 1080=2333511{}080 = 2^3 \cdot 3^3 \cdot 5^1, and 3240=2334513{}240 = 2^3 \cdot 3^4 \cdot 5^1.
Decomposing into prime factors allows direct comparison of exponents using GCD (minimum exponent) and LCM (maximum exponent) rules.
2
Analyze the GCD condition gcd(n,7200)=360\gcd(n, 7{}200) = 360.
min(a,5)=3    a=3\min(a, 5) = 3 \implies a = 3, min(b,2)=2    b2\min(b, 2) = 2 \implies b \ge 2, and min(c,2)=1    c=1\min(c, 2) = 1 \implies c = 1.
The exponent of each prime factor in gcd(x,y)\gcd(x, y) is the minimum of their respective exponents in xx and yy.
3
Analyze the LCM condition lcm(n,1080)=3240\text{lcm}(n, 1{}080) = 3{}240.
max(a,3)=3    a3\max(a, 3) = 3 \implies a \le 3, max(b,3)=4    b=4\max(b, 3) = 4 \implies b = 4, and max(c,1)=1    c1\max(c, 1) = 1 \implies c \le 1.
The exponent of each prime factor in lcm(x,y)\text{lcm}(x, y) is the maximum of their respective exponents in xx and yy.
4
Combine the exponent constraints to determine aa, bb, and cc, then calculate their sum.
a=3a = 3, b=4b = 4, and c=1c = 1, so a+b+c=3+4+1=8a + b + c = 3 + 4 + 1 = 8.
Combining a=3a=3, b2b \ge 2 with b=4b=4, and c=1c=1 with c1c \le 1 uniquely specifies (a,b,c)=(3,4,1)(a,b,c) = (3,4,1).

Anahtar Kavram

Prime Exponent Analysis of Greatest Common Divisor and Least Common Multiple
Tahmini Süre:2m 0s
Soru 15Soru

Three automated production lines—Line A, Line B, and Line C—run continuous maintenance cycles every 4545 minutes, 6060 minutes, and 7575 minutes, respectively. All three lines completed a maintenance cycle simultaneously at 8:00 a.m. on Monday. A supervisory inspection is triggered whenever at least two of the three lines complete a maintenance cycle at the exact same time. Between 8:01 a.m. on Monday and 8:00 a.m. on Tuesday, inclusive, how many supervisory inspections will be triggered?

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Cevap: 16

Cevap

16
To find the number of times at least two lines finish maintenance simultaneously, we determine the LCM for each pair of intervals (180, 225, and 300 minutes) and calculate how many multiples of these values occur within 1,440 minutes. Within this duration, there are 8 multiples of 180, 6 multiples of 225, and 4 multiples of 300. The single time all three coincide (at 900 minutes) is included in all three pairwise counts. Subtracting 2 instances of this overlap yields 8 + 6 + 4 - 2 = 16 total supervisory inspections.

Adım Adım Çözüm

1
Prime factorize each interval length
45 = 3^2 × 5; 60 = 2^2 × 3 × 5; 75 = 3 × 5^2
Prime factorization allows systematic calculation of pairwise and triple LCMs.
2
Compute pairwise and triple LCMs
lcm(45, 60) = 180; lcm(45, 75) = 225; lcm(60, 75) = 300; lcm(45, 60, 75) = 900
The LCM determines the interval between simultaneous completions.
3
Count occurrences within the 1,440-minute time window
A & B: 8 times; A & C: 6 times; B & C: 4 times; All three: 1 time
Dividing the total time window by each LCM yields the frequency of simultaneous maintenance events.
4
Apply Principle of Inclusion-Exclusion for sets
8 + 6 + 4 - 2(1) = 16 distinct inspection events
Events where all three lines coincide (at t = 900) are counted in all three pair counts and must be adjusted so that the time point is counted exactly once.

Anahtar Kavram

Least Common Multiple (LCM) and Inclusion-Exclusion Principle
Soru 16Soru

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 17Soru

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 18Soru

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 19Soru

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 20Soru

Two positive integers xx and yy have a greatest common divisor (GCD) of 1212 and a least common multiple (LCM) of 360360. Which of the following could be the value of xx? Indicate all such values.

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Cevabı ve açıklamayı göster

Cevap: 2424; 6060; 120120

Cevap

The possible values for xx are 2424, 6060, and 120120.
Any valid value of xx must be a multiple of gcd(x,y)=12\gcd(x, y) = 12 and a divisor of lcm(x,y)=360\text{lcm}(x, y) = 360. Expressing 1212 as 22312^2 \cdot 3^1 and 360360 as 2332512^3 \cdot 3^2 \cdot 5^1, xx must be of the form 2a3b5c2^a \cdot 3^b \cdot 5^c with 2a32 \leq a \leq 3, 1b21 \leq b \leq 2, and 0c10 \leq c \leq 1. The values 2424, 6060, and 120120 meet all exponent constraints.

Adım Adım Çözüm

1
Find the prime factorizations of the given GCD and LCM.
gcd(x,y)=12=223150\gcd(x, y) = 12 = 2^2 \cdot 3^1 \cdot 5^0 and lcm(x,y)=360=233251\text{lcm}(x, y) = 360 = 2^3 \cdot 3^2 \cdot 5^1.
Prime factorization allows analysis of exponent constraints for each prime factor.
2
Determine the constraints on any valid integer xx.
Any valid value of xx must be a multiple of 1212 and a factor of 360360. Specifically, x=2a3b5cx = 2^a \cdot 3^b \cdot 5^c where 2a32 \leq a \leq 3, 1b21 \leq b \leq 2, and 0c10 \leq c \leq 1.
The GCD defines the minimum exponent for each prime factor, and the LCM defines the maximum exponent.
3
Test each provided option against the prime exponent bounds.
24=233124 = 2^3 \cdot 3^1 satisfies the bounds (a=3,b=1,c=0a=3, b=1, c=0). 48=243148 = 2^4 \cdot 3^1 violates a3a \leq 3. 60=22315160 = 2^2 \cdot 3^1 \cdot 5^1 satisfies the bounds (a=2,b=1,c=1a=2, b=1, c=1). 90=21325190 = 2^1 \cdot 3^2 \cdot 5^1 violates a2a \geq 2. 120=233151120 = 2^3 \cdot 3^1 \cdot 5^1 satisfies the bounds (a=3,b=1,c=1a=3, b=1, c=1).
Options satisfying all exponent inequalities are valid possible values of xx.

Anahtar Kavram

Prime exponent properties of GCD and LCM
Sayfa 1 / 2Sonraki