To compare the two fractions, we need to make sure they have the same denominator. To do this, we find the least common multiple of 8 and 5, which is 40.

So, we rewrite the fractions with the common denominator of 40:

8 = 8 5 / 5 5 = 40 / 5

5/b = 8 b / 8 b = 8b / 8

Now we compare the fractions:

40 / 5 > 8b / 8
8 > 8b

Dividing both sides by 8:

1 > b

Therefore, b must be less than 1 for 8 / b to be smaller than 5.