Question

What is the missing number in the following sequence: 1 , 16 , _ , 100, 169?

Answer 1

The answer is 49

1 = 1 x 1

16 = 4 x 4

? = Z x Z

100 = 10 x 10

169 = 13 x 13

The “root” sequence for completion is:

1 - 4 - Z -10 - 13

The reasonable value that one can assume for “Z” is “7”: (n+1)th value = (n)th value + 3.

Hence, the number is 7 x 7 = 49.