Bunuel
If the highest common factor of 2,472, 1,284 and positive integer N is 12 and the least common multiple of the same three numbers, 2472, 1284 and N, is \(2^3*3^2*5*103*107\), what is the value of N?
(A) \(2^2 * 3^2 * 7\)
(B) \(2^2 * 3^3 * 103\)
(C) \(2^2 * 3^2 * 5\)
(D) \(2^2 * 3 * 5\)
(E) None of these
Are You Up For the Challenge: 700 Level QuestionsLet’s first factor 2,472 and 1,284 into primes:
2,472 = 12 x 206 = 2^2 x 3 x 2 x 103 = 2^3 x 3 x 103
1,284 = 12 x 107 = 2^2 x 3 x 107
We see that that the LCM of 2,472 and 1,284 is 2^3 x 3 x 103 x 107. Notice that the LCM of 2,472 1,284, and N is equal to the LCM of 2^3 x 3 x 103 x 107 and N, which is given to be 2^3 x 3^2 x 5 x 103 x 107. We are also given that the GCF of 2,472 1,284, and N is 12.
Recall that for any two positive integers a and b, we have a x b = LCM(a, b) x GCF(a, b). Therefore, by letting a = 2^3 x 3 x 103 x 107 and b = N, we have:
2^3 x 3 x 103 x 107 x N = 2^3 x 3^2 x 5 x 103 x 107 x 12
N = 3 x 5 x 12
N = 2^2 x 3^2 x 5
Answer: C