Find the missing number in the series: 5, 10, 20, 40, ?

D. 80

What is the missing number in the series: 1, 1, 2, 3, 5, ?

A. 7

Complete the series: 3, 6, 11, 18, ?

A. 25

What number should come next in the series: 10, 20, 30, 40, ?

B. 50

What is the missing number in the series: 2, 4, 8, 16, ?, 64?

A. 32