Number Series - Secretariate Exam 2015

Number Series

Normally number series questions came from 2 different categories.

Type I

 Adding/Subtracting a constant (or constantly varying) value to each number in the series to get the next number.

Easy

Eg. 1  5  9  13 17…. Here first number 1 is added with a constant value 4 to get the second number and so on

 1+4 =5

5+4 =9

9+4=13

Eg. 100  88 76 64…. Here constant value 12 is subtracted from first number 100 to get the next number in the series and so on

100 -12 = 88

88 – 12 = 76

76 – 12 = 64

Moderate

2, 7, 17, 32, 52 … Here 5 is added to first number 2 to get the next number in the series and 10(ie.5x2) is added to second number to get next number and so on. (2013 Sec.Asst Qn)

2 + (5x1) = 7

7 + (5x2) = 17

17 + (5x3) = 32

32 + (5x4) = 52

Difficult

Eg. 1,  5,  14,  30 …. Here first number 1 is added with square of 2 and second number is added with square of 3 and so on

 1+2² =5

5+3² =14

14+4²=30

Type II

 Multiply/ Divide a value with each number in the series to get the next number.

Easy

Eg. 1, 6, 36, 216, 1296…. Here each number is multiplied with 6 to get the next number in the series.

 1 x 6 = 6

6 x 6 = 36

36 x 6 = 216

216 x 6 = 1296

Eg. 120, 60, 30, 15…. Here first number, 120, is divided with a constant value 2 to get the second number and so on

 120/2 = 60

60/2 = 30

30/2=15

Moderate

Eg.  4, 8, 24, 96 … Here, 2 is multiplied with first number 4 to get next number 8 and 3 is multiplied with 8 to get third number 24 and so on

4 x 2 = 8

8 x 3 = 24

24 x 4 = 96

Difficult

Eg. 3, 3, 12, 108 … Here square of 1 is multiplied with first number 3 to get next number and square of 2 is multiplied with second number 3 to get next number and so on

3 x (1²) = 3

3 x (2²) = 12

12 x (3²) = 108