Question

Identify the term that will replace the ?

$1,3,3,6,7,9,7,?,12,21$

• A. $10$
• B. $11$
• C. $12$
• D. $13$

Answer 1

The correct option is D $13$

Clearly, the given sequence is a combination of two series;
(I) $1,3,7,?,21$ and (II) $3,6,9,12$
The pattern followed in I is $+2,+4$, ........ and the pattern followed in II is $+3$.
So, missing number $=7+6=13$.
Hence, the answer is (D).