What number would replace the question mark in the series 3, 6, 11, 20, 37, 70, 135, 264, ?

A399

B421

C521 ✓ Correct

D489

Correct answer: (C) 521

Explanation

The next term is 521.

Each term = 2 times the previous term minus a rising count.

2 x 6 - 1 = 11; 2 x 11 - 2 = 20; 2 x 20 - 3 = 37.

2 x 37 - 4 = 70; 2 x 70 - 5 = 135; 2 x 135 - 6 = 264.

2 x 264 - 7 = 521.

Want more like this? Create a free account to practise a full test, track your progress, and get spaced-repetition review.