Explanation: 440, 360, 288, 224, = 21^2 – 1, 19^2 – 1, 17^2 – 1, 15^2 – 1, _____ = The given numbers can be expressed in the form of n^2 – 1 of consecutive odd numbers starting from 21^2 – 1. Hence the next number in the series is 13^2 - 1 = 168