6, 11, 21, 36, 56, ?
what will replace the question mark in the series ?

Answer: Option D

Explanation:

We can see the given series is in G.P.
as 2*3 = 6, 6*3 = 18, 18*3 = 54
So a = 2 , r = 3
nth term in G.P. is
\begin{aligned}
ar^{n-1} \\
= 2*3{8-1} \\
= 2*3^7 \\
= 2*2187 = 4374
\end{aligned}

Answer: Option B

Explanation:

Pattern is , +5, +7, +9
Missing Number = 19+9 = 28

Answer: Option C

Explanation:

The terms of the given series are numbers formed by joining together consecutive odd numbers in order i.e. 1 and 3, 3 and 5, 5 and 7, 7 and 9, 9 and 11, .....

So, missing term = number formed by joining 11 and 13 = 1113.

Answer: Option C

Explanation:

In this series the pattern is +4, +8, +12, +16, so next will be +20

Term which will replace the question mark in this series will be 45+20 = 65

Answer: Option D

Explanation:

Pattern in the series is -1, -2, .., .. , -5

So next term will be 17 - 3 = 14