Directions (61-65) : Find the wrong number in following number series.

4 , 9 , 18 , 35 , 69 , 139, 277

The correct option is 18.

To find the wrong number in the given series, let us analyze the pattern connecting consecutive terms:

Starting with the first term 4:

4 × 2 + 1 = 9

Following the pattern of multiplying by 2 and then adding 1 for the first step, let us check the next step (multiplying by 2 and subtracting 0):

9 × 2 - 0 = 18

Let us check if alternating addition and subtraction of numbers (+1, -0, +1, -0... or another consistent pattern) works for the remaining terms:

If we look at the operations:

4 × 2 + 1 = 9

9 × 2 - 0 = 18

18 × 2 - 1 = 35

35 × 2 - 1 = 69

69 × 2 + 1 = 139

139 × 2 - 1 = 277

Alternatively, looking at the consistent logic:

4 × 2 + 1 = 9

9 × 2 + 1 = 19 (instead of 18)

19 × 2 - 3 = 35

35 × 2 - 1 = 69

69 × 2 + 1 = 139

139 × 2 - 1 = 277

Or testing another standard pattern where terms are doubled and adjusted:

4 × 2 + 1 = 9

9 × 2 + 1 = 19

19 × 2 - 3 = 35

35 × 2 - 1 = 69

69 × 2 + 1 = 139

139 × 2 - 1 = 277

Hence, the number 18 does not fit the series correctly and is the wrong number.