Reasoning | Series

Series questions in reasoning are basically of two types, Series completion (missing term, next term) and Series correction (finding the wrong element in the series).

Sample Problems

Question 1 : Find the missing term : 157.5, 45, 15, _, 3, 2, 2
Solution : Le the missing number be ‘n’
157.5 / 45 = 3.5
45 / 15 = 3
15 / n = 2.5
n / 3 = 2
3 / 2 = 1.5
2 / 2 = 1
Therefore, the missing number is 6.

Question 2 : Find the next term in the series : 6, 7, 9, 13, _
Solution : Let the missing number be ‘n’
7 – 6 = 1
9 – 7 = 2
13 – 9 = 4
n – 13 = 8
Therefore, next number in the series = n = 21

Question 3 : Find the incorrect element in the series : 1, 3, 10, 36, 152, 760, 4632
Solution : 
1 x 1 + 2 = 3
3 x 2 + 4 = 10
10 x 3 + 6 = 36
36 x 4 + 8 = 152
152 x 5 + 10 = 770
770 x 6 + 12 = 4632
Therefore, the incorrect element in the series is 760.