Question

In the following number series, only one number is wrong. Find out the wrong number. 7, 4, 5, 9, 20, 51, 160.5.
Options : 4, 5, 9, 51.

Answer 1

The wrong number is 51.

7 * .5 + .5 = 4,

4 * 1 + 1 = 5,

5 * 1.5 + 1.5 = 9,

9 * 2 + 2 = 20,

20 * 2.5 + 2.5 = 52.5,

52.5 * 3 + 3 = 160.6.

So, the wrong number is 51.