Directions (36-40) : What value comes in place of the question mark (?) in the following series?
52, 56, ?, 108, 172, 272
88
82
72
68
None of these
Solution
$ 52 + 2^2 = 52 + 4 = 56$
$56 + 4^2 = 56 + 16$ = 72
$72 + 6^2 = 72 + 36 = 108$
$108 + 8^2 = 108 + 64 = 172$
$172 + 10^2 = 172 + 100 = 272$