Question

Look at this series $21,9,21,11,21,13,...$ What number should come next ?

• A. $14$
• B. $15$
• C. $21$
• D. $23$

Answer 1

The correct option is C

$21$

Explanation of the correct option.

Compute the next number of the series.

Given: $21,9,21,11,21,13,...$

The fourth term of the series can be derived by adding $2$ in the second term,

$11=9+2$

The sixth term of the series can be derived by adding $2$ in the fourth term,

$13=11+2$

We can see that in the given series random number $21$ is repeated alternately or at each odd's place.

Hence, the next number of the series is $21.$

Option $\left(C\right)$ is the correct answer.