Question

which digit will come in the place of question mark:
1, 2 ,6 ,15 , ? ,56.

Answer 1

Answer:

31

Becz

1 + (1) ^2 = 2

2 + (2) ^2 = 6

6 + (3) ^2 =15

15+ (4) ^2 = 31

31 + (5) ^2 = 56

Answer 2

Answer:

2-1=1

6-2=4

15-6=9

31-15=16

56-31=25

answer is : 31