If a, b, c, d and e are integers and p = 2^a3^b and q = 2^c3^d5^e, is p/q a terminating decimal?
(1) a > c
(2) b > d
For a fraction to have a terminating decimal, the numerator must be an integer and the denominator must be only powers of 2s and/or 5s. We have the fraction 2^a3^b/2^c3^d5^e. The numerator is okay, because we know it will be an integer. The denominator must be only powers of 2s and/or 5s, so we need to see if we can cancel the 3^d for the fraction to be terminating. The only way to get rid of the 3^d in the denominator would be for the power of 3^b in the numerator to be larger than 3^d in the denominator. When an integer raised to a power in the numerator is larger than the same integer raised to a power in the denominator, we can subtract/cancel the denominator. For instance, 2^4/2^3 is simply 2^1. Thus, we need to see if 3^b is greater than 3^d, so we need to ask: b>d?
So, back to the question.
1) Doesn't tell us anything about b>d. There is still a 3 in the denominator, so we won't be able to prove whether this is a terminating decimal or not. INSUFFICIENT
2) This is exactly what we are looking for. We know that b>d, so we know that the 3^d in the denominator will go away, thus leaving only powers of 2 and 5 in the denominator, making this fraction a terminating decimal. SUFFICIENT.
Answer (B).