Question

Help Smith find out the next two numbers of the series:
8, 12, 9, 13, 10, 14, 11, __, __

• A. 12; 17
• B. 17; 12
• C. 12; 15
• D. 15; 12

Answer 1

The correct option is D 15; 12

Smith has 8, 12, 9, 13, 10, 14, and 11 in the series.

This number series is an alternating addition and subtraction series.

In this series:
$8\stackrel{+4}{\to 12}\stackrel{-3}{12\to 9}\stackrel{+4}{9\to 13}13\stackrel{-3}{\to 10}10\stackrel{+4}{\to 14}14\stackrel{-3}{\to 11}11\stackrel{+4}{\to 15}15\stackrel{-3}{\to 12}$

So, the next two numbers in the series will be 15 and 12.