2009 AMC 12A Problem 6

Below is the professionally curated solution for Problem 6 of the 2009 AMC 12A, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2009 AMC 12A solutions, or check the answer key.

All of the real AMC 8, AMC 10, AMC 12, and AIME problems in our complete solution collection are used with official legal permission of the Mathematical Association of America (MAA).

Concepts:exponentsubstitution

Difficulty rating: 1290

6.

Suppose that P=2mP = 2^m and Q=3n.Q = 3^n. Which of the following is equal to 12mn12^{mn} for every pair of integers (m,n)?(m, n)?

P2QP^2 Q

PnQmP^n Q^m

PnQ2mP^n Q^{2m}

P2mQnP^{2m} Q^n

P2nQmP^{2n} Q^m

Solution:

Since 12=223,12 = 2^2 \cdot 3, 12mn=22mn3mn=(2m)2n(3n)m=P2nQm.12^{mn} = 2^{2mn} \cdot 3^{mn} = (2^m)^{2n}(3^n)^m = P^{2n}Q^m.

Thus, the correct answer is E.

Problem 6 in Other Years