2007 AMC 10A Problem 17

Attempt Problem 17 of the 2007 AMC 10A below, then check your answer against the professionally curated solution from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2007 AMC 10A solutions, or check the answer key.

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17.

Suppose that mm and nn are positive integers such that 75m=n3.75m = n^3. What is the minimum possible value of m+n?m + n?

1515

3030

5050

6060

57005700

Answer: D
Concepts:perfect powerprime factorization
Difficulty rating: 1480
Solution:

Since n3=75m=352m,n^3 = 75m = 3 \cdot 5^2 \cdot m, every prime factor must occur a multiple of three times.

The smallest such mm is 325=45,3^2 \cdot 5 = 45, giving n3=3353n^3 = 3^3 \cdot 5^3 and n=15.n = 15.

Then m+n=45+15=60.m + n = 45 + 15 = 60.

Thus, the correct answer is D.

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