What number can replace the question mark in the series 2, 4, 7, 12, 21, 38, ?

A67

B61

C50

D71 ✓ Correct

Correct answer: (D) 71

Explanation

The missing term is 71.

differences are 2, 3, 5, 9, 17.

these grow by 1, 2, 4, 8, doubling each time.

next gap = 17 + 16 = 33.

38 + 33 = 71.

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