**Number Series**

Number Series is a sequence formed out of numbers. In the number series questions. We will have to detect the rules that result in the formation of a number series. These series are of many kinds and so are the questions that may appear from these topics.

**Look carefully for the pattern, and then choose which pair of numbers comes next.**

**1) 28 25 5 21 18 5 14**

A. 11 5

B. 10 7

C. 11 8

D. 5 10

E. 10 5

**Answer**: Option A

**Explanation**: This is an alternating subtraction series with the interpolation of a random number, 5, as every third number. In the subtraction series, 3 is subtracted, then 4, then 3, and so on.

**2) 8 11 21 15 18 21 22**

A. 25 18

B. 25 21

C. 25 29

D. 24 21

E. 22 26

**Answer**: Option B

**Explanation**: This is an alternating addition series, with a random number, 21, interpolated as every third number. The addition series alternates between adding 3 and adding 4. The number 21 appears after each number arrived at by adding 3.

**3) 9 16 23 30 37 44 51**

A. 59 66

B. 56 62

C. 58 66

D. 58 65

E. 54 61

**Answer**: Option D

**Explanation**: Here is a simple addition series, which begins with 9 and adds 7.

**4) 2 8 14 20 26 32 38**

A. 2 46

B. 44 50

C. 42 48

D. 40 42

E. 32 26

**Answer**: Option B

**Explanation**: This is a simple addition series, which begins with 2 and adds 6.

**5) 9 11 33 13 15 33 17**

A. 19 33

B. 33 35

C. 33 19

D. 15 33

E. 19 21

**Answer**: Option A

**Explanation**: In this alternating repetition series, a random number, 33, is interpolated every third number into a simple addition series, in which each number increases by 2.

**6) 2 3 4 5 6 4 8**

A. 9 10

B. 4 8

C. 10 4

D. 9 4

E. 8 9

**Answer**: Option D

**Explanation**: This is an alternating addition series with a random number, 4, interpolated as every third number. In the main series, 1 is added, then 2 is added, then 1, then 2, and so on.

**7) 17 17 34 20 20 31 23**

A. 26 23

B. 34 20

C. 23 33

D. 27 28

E. 23 28

**Answer**: Option E

**Explanation**: This is an alternating subtraction series with repetition. There are two different patterns here. In the first, a number repeats itself; then 3 is added to that number to arrive at the next number, which also repeats. This gives the series 17, 17, 20, 20, 23, and so on. Every third number follows a second pattern, in which 3 is subtracted from each number to arrive at the next: 34, 31, 28.

**8) 6 20 8 14 10 8 12**

A. 14 10

B. 2 18

C. 4 12

D. 2 14

E. 14 14

**Answer**: Option D

**Explanation**: This is an alternating addition and subtraction series. In the first pattern, 2 is added to each number to arrive at the next; in the alternate pattern, 6 is subtracted from each number to arrive at the next.

**9) 21 25 18 29 33 18**

A. 43 18

B. 41 44

C. 37 18

D. 37 41

E. 38 41

**Answer**: Option D

**Explanation**: This is a simple addition series with a random number, 18, interpolated as every third number. In the series, 4 is added to each number except 18, to arrive at the next number.

**10) 75 65 85 55 45 85 35**

A. 25 15

B. 25 85

C. 35 25

D. 85 35

E. 25 75

**Answer**: Option B

**Explanation**: This is a simple subtraction series in which a random number, 85, is interpolated as every third number. In the subtraction series, 10 is subtracted from each number to arrive at the next.

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