Bunuel
Any decimal that has only a finite number of nonzero digits is a terminating decimal.
For example, 10, 0.23, and 8.107 are three terminating decimals. If n and m are positive integers and the ratio n/m is expressed as a decimal, is n/m a terminating decimal?
(1) n is a three-digit number divisible by 10.
(2) m = 5
Official Explanation
This question takes some time to define a terminating decimal and asks us whether n/m such a decimal is. Let's look at the statements, separately first.
Statement (1) tells us that n is a number such as 200 or 210. Meanwhile, m could be any positive integer, such as 3. We get a terminating decimal from n/m = 210/3 = 70, but not from 200/3, which will have a repeating 3. Therefore, the possible cases include conflicting possible answers, and Statement (1) is insufficient.
Statement (2) tells us that m is 5. Meanwhile, we know nothing about n, except that it's a positive integer. If n=10, then n/m = 10/5 = 2, and we have a terminating decimal. If n=3, then n/m = 3/5 = 0.6. That, too, is a terminating decimal. No matter what n is, when divided by m it will be an integer or end in .2, .4, .6, or .8. Therefore, n/m will also be a terminating decimal. We can answer definitively, so Statement (2) is sufficient.
The correct answer is (B).