In following question, a number series is given with one term missing. Choose the correct alternative that will same pattern and fill in the blank spaces. -
5, 6, 9, 15, , 40
Answer: B. 25
The pattern is + 1, + 3, + 6,... i.e. + 1, + (1 + 2), + (1 + 2 + 3),...
.'. Missing number = 15 + (1 + 2 + 3 + 4) = 25.