Find the next number in the series: 9, 13, 21, 37, 69, ?

Correct option is D

Ans. (a)
Sol. The difference between consecutive terms increases as follows:
· 13 - 9 = 4
· 21 - 13 = 8
· 37 - 21 = 16
· 69 - 37 = 32 The difference doubles each time. The next difference should be 64, and adding this to 69 gives 133.
Explanation of each option:
· (a) 127 – Incorrect. The correct next number is 133, not 127.
· (b) 131 – Incorrect.
· (c) 129 – Incorrect.
· (d) 133 – Correct answer.