In the following series one number is wrong, Find out the wrong number. 9, 12, 71, 158, 259, 368, 478.5

In the following series one number is wrong, Find out the wrong number.

9, 12, 71, 158, 259, 368, 478.5

The pattern is as follows:

Taking difference

⇒ 12 – 9 = 3

⇒ 71 – 12 = 59

⇒ 158 – 71 = 87

⇒ 259 – 158 = 101

⇒ 368 – 259 = 109, (367 – 259 = 108)

⇒ 478.5 – 368 = 110.5 (478.5 – 367 = 111.5)

Taking difference again

⇒ 59 – 3 = 56

⇒ 87 – 59 = 28

⇒ 101 – 87 = 14

⇒ 109 – 101 = 8 (108 – 101 = 7)

⇒ 110.5 – 109 = 1.5 (111.5 – 108 = 3.5)

As we can observe the next number after the difference is half the previous.

But due to 368 the series is not following the pattern.

∴ 368 is wrong and should be replaced by 367.

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