Question

Find the number at the place of ?: 1,2,6,?,31,56

Answer 1

It's very simple ,

The answer is 15,

Reason :

Let the ? = x,

=> Series : 1,2,6,x,31,56,

Now take out differences for each,

We get,
1, 4, x-6, 31-x, 25,

If we observe 1,4,25, They are perfect squares,

So by my guess, x-6 and 31-x must also be perfect Squares,

The only perfect squares between 4 and 25 are 9 and 16,

So, x-6 = 9 => x = 15,
and 31-x = 16 => x = 15,

Therefore the answer is 15, as differences are perfect squares !

Hope you understand, Have a great day !
Thanking you, Bunti 360 !!