Data Sufficiency

Any decimal that has only a finite number of nonzero digits is a terminating decimal. For example, 24, 0.82 and 5.096 are three terminating decimals. If r and s are positive integers and the ratio r/s is expressed as a decimal, is r/s a terminating decimal?

(1) 90 < r < 100
(2) s = 4

Please explain your solution, I'm posting this question here because
(a) OG explanation did not make sense to me.
(b) I want to know how to approach these type of problems.