In the series 3, 9, 15.. what will be the 21st term ?

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 D

Explanation:

Series is having pattern
\begin{aligned}
3*1^2, 3*2^2, 3*3^2, ......\\
\text{Next will be } 3*7^2 = 147
\end{aligned}

Answer: Option B

Explanation:

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

Answer: Option A

Explanation:

Pattern in the series is, -2, -4, -2, -4. So next term will be -2
24 -2 = 22

Answer: Option C

Explanation:

Pattern for the given series is, +8, +8, +16, +16, +24

So next will be +24, 73+24 = 97