What is the smallest positive integer n such that, out of the n unit fractions 1/k where 1 < k < n, exactly half of the fractions give a terminating decimal?
I'm not sure if I understand your question properly. But, I think the smallest positive integer n =8.
So that: 1/2, 1/3, 1/4, 1/5, 1/6, 1/7, exactly half give terminating decimal, namely:
1/2, 1/4, 1/5, and the other half don't, namely: 1/3, 1/6, 1/7.
