In the following question, select the missing number from the given series :
1, 4, 3, 16, 6, 36, 10, 64, 15, 100, ?

Options

A. 21
B. 19
C. 22
D. 25

Answer

A

Explanation

There are two alternating series ,
(i) 1 + 2 = 3
3 + 3 = 6
6 + 4 = 10
10 + 5 = 15
15 + 6 = 21
(ii) 4 + 12 = 16
16 + 20 (= 12 +8) = 36
36 + 28 (= 20 +8) = 64
64 + 36 (= 28 +8) = 100