# Placements | 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.

Please write comments if you have any doubts related to the topic discussed above, or if you are facing difficulty in any question or if you would like to discuss a question other than those mentioned above.