Which number comes next in the falling series 120, 99, 80, 63, 48, ?

Explanation

1. 01

   Differences: 21, 19, 17, 15, falling by 2, so the next difference is 13 and $48 - 13 = 35$.

2. 02

   Check: the terms are $11^2 - 1, 10^2 - 1, 9^2 - 1, 8^2 - 1, 7^2 - 1$, so the next is $6^2 - 1 = 35$.