# Number Series Aptitude Q & A – Part 1

*This is the Part 1 Aptitude Questions and Answers section on “Number Series” with explanation for various interview, competitive examination and entrance test. Solved examples with detailed answer description, explanation are given and it would be easy to understand. *

**1. Look at this series: VI, 10, V, 11, __, 12, III, … What number should fill the blank?**

A. II

B. IV

C. IX

D. 14

**Answer:**

B. IV

**Explanation:**

This is an alternating addition and subtraction series. Roman numbers alternate with Arabic numbers. In the Roman numeral pattern, each number decreases by 1. In the Arabic numeral pattern, each number increases by 1.

**2. Look at this series: (1/9), (1/3), 1, ____ , 9, … What number should fill the blank?**

A. (2/3)

B. 3

C. 6

D. 27

**Answer:**

B. 3

**Explanation:**

This is a multiplication series; each number is 3 times the previous number.

**3. 32 29 26 23 20 17 14**

A. 11 8

B. 12 8

C. 11 7

D. 32 29

**Answer:**

A. 11 8

**Explanation:**

In this simple subtraction series, the numbers decrease by 3.

**4. 16 26 56 36 46 68 56**

A. 80 66

B. 64 82

C. 66 80

D. 78 68

**Answer:**

C. 66 80

**Explanation:**

Here, every third number follows a different pattern from the main series. In the main series, beginning with 16, 10 is added to each number to arrive at the next. In the alternating series, beginning with 56, 12 is added to each number to arrive at the next.

**5. 9 12 11 14 13 16 15**

A. 14 13

B. 18 21

C. 14 17

D. 18 17

**Answer:**

D. 18 17

**Explanation:**

This is a simple alternating addition and subtraction series. First, 3 is added, then 1 is subtracted, then 3 is added, 1 subtracted, and so on.

**6. 4 8 22 12 16 22 20 24**

A. 28 32

B. 28 22

C. 22 28

D. 32 36

**Answer:**

C. 22 28

**Explanation:**

This is an alternating repetition series, with a random number, 22, interpolated as every third number into an otherwise simple addition series. In the addition series, 4 is added to each number to arrive at the next number.

**7. 2 8 14 20 26 32 38**

A. 2 46

B. 44 50

C. 42 48

D. 40 42

**Answer:**

B. 44 50

**Explanation:**

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

**8. 9 11 33 13 15 33 17**

A. 19 33

B. 33 35

C. 33 19

D. 15 33

**Answer:**

A. 19 33

**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.

**9. Look at this series: 1.5, 2.3, 3.1, 3.9, … What number should come next?**

A. 4.2

B. 4.4

C. 4.7

D. 5.1

**Answer:**

C. 4.7

**Explanation:**

In this simple addition series, each number increases by 0.8.

**10. Look at this series: 14, 28, 20, 40, 32, 64, … What number should come next?**

A. 52

B. 56

C. 96

D. 128

**Answer:**

B. 56

**Explanation:**

This is an alternating multiplication and subtracting series: First, multiply by 2 and then subtract 8.

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