DAY 91

Comment

The numbers in the second pair are both 0.1 more than the numbers in the first pair.
Imagine they were, say, 1 bigger (so you are comparing 21 divided by 5 and 22 divided by 6).

Answer

21 divided by 5 is larger than 21.1 divided by 5.1.

Readers' methods

Ilan A, Neve Monosson, Israel:
21/5 is larger.
Since 21 > 5 you cannot add the same to the numerator and denominator
and keep the same ratio;
you have to add to the numerator 21/5 times what you add to the denominator
to keep equality.