Let us assume that the fractions are 1/2 and 1/5. 1/5 has the larger denominator. By converting them to decimal,
1/2 = 0.5
1/5 = 0.2
We can see that 0.2 is smaller than 0.5. This also means that 1/5 is smaller than 1/2. This is so because for the larger denominator, the numerator is divided into smaller pieces compared to when it is divided by the smaller denominator. Thus, Olivia's reasoning is correct.