Alan rewrites a fraction less than 1 as a decimal. The numerator is a whole number greater than 0. For which denominator will the fraction always convert to a terminating decimal?

The answer is D) 16

The reason why is because 16 = 2*2*2*2 has only 2 as its prime factor. Any time 2 or 5 are the prime factors of the denominator, then the decimal will terminate. Examples include fractions like 1/2, 1/5, 1/10