Find the odd number in the series 63, 48, 34, 24, 15, 8, 3

The correct answer is Option (2) → 34

The terms are one less than the squares of 8, 7, 6, 5, 4, 3 and 2, that is \(n^2-1\):

• \(8^2-1=63\), \(7^2-1=48\)

• \(6^2-1=35\), but the series has 34

• \(5^2-1=24\), \(4^2-1=15\), \(3^2-1=8\), \(2^2-1=3\)

Every other term fits, so 34 is the wrong number; it should be 35. The differences show the same thing: with 35 they run 15, 13, 11, 9, 7, 5.