In following number series, two terms have been put within brackets. Choose the appropriate option
Look at this series: 3, 4, 7, 8, 11, 12, . . . What number should come next ?
Option:
A. 7
B. 10
C. 14
D. 15
Answer: D . 15
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Justification:
This alternating addition series begins with 3;
then 1 is added to give 4;
then 3 is added to give 7;
then 1 is added, and so on.
Rule = (first number + 1) (second number + 3) (third number + 1) (fourth number + 3)...
Now The series is 3, 4, 7, 8, 11, 12...
(3 + 1 = 4), (4 + 3 = 7), (7 + 1 = 8), (8 + 3 = 11), (11 + 1 = 12) (12 + 3 = 15)...
So the answer is d = 15.
