2009 AMC 10A Problem 13 — Solution | LIVE by Po-Shen Loh

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2009 AMC 10A Problem 13

Attempt Problem 13 of the 2009 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 2009 AMC 10A solutions, or check the answer key.

All problems are used with official legal permission of the Mathematical Association of America (MAA).

13.

Suppose that $P = 2^m$ and $Q = 3^n.$ Which of the following is equal to $12^{mn}$ for every pair of integers $(m, n)?$

$P^2 Q$

$P^n Q^m$

$P^n Q^{2m}$

$P^{2m} Q^n$

$P^{2n} Q^m$

Answer: E

Concepts:exponent prime factorization

Difficulty rating: 1280

Solution:

Since $12 = 2^2 \cdot 3,$ $\begin{aligned} 12^{mn} &= 2^{2mn} \cdot 3^{mn} \\ &= (2^m)^{2n} \cdot (3^n)^m \\ &= P^{2n} Q^m. \end{aligned}$

Thus, the correct answer is E.

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