Question

Find the next two terms of the sequence: $4,13,8,17,12,21,...$

• A. $16,21$
• B. $20,21$
• C. $16,25$
• D. $16,11$

Answer 1

The correct option is C $16,25$

$\underset{–}{ConceptInvolved:}$

Second term is obtained by adding $9$ to the first term. Third term is obtained by subtracting $5$ from the second term and the pattern continues.

$\underset{–}{Method:}$

First term $=4$
Second term:
$4+9=13$
Third term:
$13-5=8$
Fourth term:
$8+9=17$
Fifth term:
$17-5=12$
Sixth term:
$12+9=21$
Seventh term:
$21-5=16$
Eighth term:
$16+9=25$

Next two terms after $21$ would be $16$ and $25$ respectively which are obtained by following the pattern observed in the question.