You have a good point; we usually simplify fractions when possible! Here, however, if we simplified 4/10 to 2/5, for example, then it would seem to say that we made only 5 attempts, when we really made 10 attempts. We simplify when we are about the ratio between two numbers, not so much the value of the numbers. In this problem, the number of initial attempts was fixed, and we are trying to figure out how much the numerator and denominator need to increase by (x, which is 4).
The Daily Challenge Team