What number would replace the question mark in the series 1, 4, 3, 5, 6, 9, 13, 20, 31, ?

A49 ✓ Correct

B51

C47

D45

Correct answer: (A) 49

Explanation

The next term is 49.

Each term = 2 times the previous term minus the term three places earlier.

Check with 31: 2 x 20 - 9 = 31.

For the next term: 2 x 31 - 13 = 62 - 13.

= 49.

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