Question

What will come in place of question mark (?) in the following number series?

8, 12, 26, 55, 104, ?

1. 178
2. 108
3. 148
4. 170
5. 128

Answer 1

Correct Answer - Option 1 : 178

Considering the above series,

8, 12, 26, 55, 104, ?

The logic of the series can be explained as,

12 - 8 = 4

26 - 12 = 14

55 - 26 = 29

104 - 55 = 49

? - 104 = let's say x

Taking double difference,

14 - 4 = 10

29 - 14 = 15

49 - 29 = 20

By observing the pattern of double difference, we can write

x - 49 = 25

⇒ x = 74

So, ? - 104 = 74

⇒ ? = 178

∴ The value of ? is 178