Bunuel wrote:

If n is the smallest integer such that 432 times n is the square of an integer, what is the value of n?

(A) 2

(B) 3

(C) 6

(D) 12

(E) 24

IMPORTANT CONCEPT: The

prime factorization of a perfect square (the square of an integer) will have an

even number of each primeFor example: 400 is a perfect square.

400 = 2x2x2x2x5x5. Here, we have four 2's and two 5's

This should make sense, because the even numbers allow us to split the primes into two EQUAL groups to demonstrate that the number is a square.

For example: 400 = 2x2x2x2x5x5 = (2x2x5)(2x2x5) = (2x2x5)²

Likewise, 576 is a perfect square.

576 = 2X2X2X2X2X2X3X3 = (2X2X2X3)(2X2X2X3) = (2X2X2X3)²

------NOW ONTO THE QUESTION!!------------------------

Give: 432n is a perfect square

Let's find the prime factorization of 432

We get:

432 = (2)(2)(2)(2)(3)(3)(3)So, the prime factorization of 432 has four 2's and three 3's

We already have an EVEN number of 2's. So, if we add one more 3 to the prime factorization, we'll have an EVEN number of 3's

So, if

n = 3, then 432n =

(2)(2)(2)(2)(3)(3)(3)(

3)

Since 432n has an EVEN number of each prime, 432n must be a perfect square.

Answer:

Cheers,

Brent

_________________

Brent Hanneson – Founder of gmatprepnow.com