1,6,15,(...),45,66,91

Answer: Option B

Explanation:

Pattern is +3,+4,..,..,+7, so +5 and +6 will be in the blanks

Question mark will be replaced by 9+5 = 14

Answer: Option A

Explanation:

Series Pattern is +3, +5, +7, +9.

So next number = 25+11 = 36

Answer: Option B

Explanation:

Pattern in the series is, +20.5 , +22.5,
Next will be +24.5
138 + 24.5 = 162.5

Answer: Option D

Explanation:

In this series, each term is the sum of preceding two terms as,
1+2 = 3
3+2 = 5
5+3 = 8
Next term in the series will be,
8+5 = 13

Answer: Option A

Explanation:

We can judge that it is A.P.
With 6 as difference
nth term in A.P. = a+(n-1)d
a= 3, n = 21, d = 6
So, 21st term will be = 3+(20)6 = 123