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

Explanation

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.