# Number Series Questions and Answers – I

17 questions on “number series questions and answers series” related where one number is missing and you have to find the missing number.

Benefits of such type of questions is that these are asked every now and then in almost every exam be it: competitive exams, UPSC, Bank PO, CAT, job interviews etc.

Also, it is a good exercise to keep ones brain sharp and their calculation power good. Please have a look at it and let us know your thoughts on this.

Other similar articles: Part – I | Part – II | Part– III | Part – IV | Part – V | Part – VI | Part – VII | Part – VIII | Part – IX | Part – X.

Odd Man out: Part – I | Part II.

## Questions Section:

Q1. Here is the number series to solve, if:
59 + 86 = 8555
30 + 75 = 3150
100 + 89 = 18900
37 + 60 = ???

Find the missing number.

30*(30+75) = 3150

Logic: The logic is addition of both number multiplied by first number i.e.(59 + 86)*59=8555

Q2. Second question in the series is:
31 + 6 = 775
17 + 47 = -510
24 + 48 = -576
29 + 79 = ???

what will be the missing number?

(17-47)*17 = -510

Logic: The logic is subtraction of both number multiplied by first number i.e.(31 – 6)*31=775

Q3. Third question in the series is:
10 + 59 = 79
36 + 6 = 78
95 + 40 = 230
33 + 51 = ???

– what will be the missing number here?
Answer: 117 i.e. 2*33 + 51

2*36 + 6 = 78

Logic: The logic is 2 multiplied by first number plus second number i.e.(10*2 + 59)=79.

Q4. What is the next number in the series:

42 , 21.0 , 10.5 , 5.25 , ?

Ans. 2.625

42/2, 21/2, 10.5/2 and 5.25/2.

Logic: Second number is half of first one, 3rd number is half of second one and so on i.e.42/2, 21.0/2 and so on.

Q5. Guess next number in the series:

44, 22.0 , 11.0 , 5.5 , ?

Ans. 2.75 i.e. 5.5/2

44/2, 22/2, 11/2 and 5.5/2.

Logic: Second number is half of first one, 3rd number is half of second one and so on i.e.44/2, 22.0/2 and so on.

Q6. Guess next number in the series:

8, 64 , 512 , 4096 , ?

Ans. 32,768.

i.e. 8^1, 8^2, 8^3, 8^4 and 8^5.

Logic: The series is square, cube, ^4 and so on i.e. 8*8 , 8*8*8 etc.

Q7. What’s the next number in the series:

2 , 4 , 8 , 16 , ?

Ans. 32 i.e. 16*2 or 2^5

2, 2*2 = 4, 2*2*2 = 8, 2*2*2*2 = 16 and 2*2*2*2*2 = 32

Logic: The series is square, cube, ^4 and so on i.e. 2, 2*2, 2*2*2 and so on.

Q8. Guess the next number in the series:

4 , 5 , 7 , 10 , ?

Ans. 14 i.e. 10 + 4

4 + 1 = 5, 5 + 2 = 7, 7 + 3 = 10 and 10 + 4 = 14

Logic: Second number is (1st number + 1), third number is (2nd number + 2), 4th is (3rd number + 3) and so on.

Q9. What will be the next number in the series:

13 , 15 , 19 , 25 , ?

Ans. 33 i.e. 25 + 8

13 + 2 = 15, 15 + 4 = 19, 19 + 6 = 25 and 25 + 8 – 33
Logic: Second number is (1st number + 2), third number is (2nd number + 4), 4th is (3rd number + 6) and so on.

Q10. Find the missing number in the series:

6 , 8 , ?? , 18 , 26, 36

Ans. 12 i.e.8 + 4
6+2=8 , 8+4=12 , 12+6=18 , 18+8=26, 26+10=36.
Logic: Second number is (1st number + 2), third number is (2nd number + 4), 4th is (3rd number + 6) and so on.

Q11. Identify the missing number in the series:

28 , 31 , ?? , 37 , 40 , 43

Ans. 34 i.e.31 + 3.
28+3=31,31+3=34,34+3=37,37+3=40,
Logic: Second number is (1st number + 3), third number is (2nd number + 3), 4th is (3rd number + 3) and so on.i.e. every other number is previous number plus 3.

Q12. Identify the missing number in the series:

20 , 23 , ?? , 32 , 38 , 45

Ans. 27 i.e.23 + 4
20+3=23,23+4=27,27+5=32,32+6=38,38+7=45.
Logic: First number + 3 = 2nd number, second number + 4 = 3rd number, third number + 5 = 4th number and so on.

Q13. Find the missing number in the series:

2 , 2 , ?? , 12 , 48 , 240

Ans.4 i.e. 2*2=4.

2*1=2 , 2*2=4 , 4*3=12 , 12*4=48 , 48*5=240.
Logic: First number1 = 2nd number, second number2 = 3rd number, third number*3 = 4th number and so on.

Q14. Find the missing number in the series:

14 , 29 , 43 , ?? , 71 , 85

Ans.57 i.e.(14*4+1)=57

14*2+1=29 , 14*3+1=43 , 14*4+1=57 , 14*5+1=71 , 14*6+1=85.
Logic: 1st number *2 + 1 = second, 1st number * 3 + 1 = third and so on.

Q15. Find the missing number in the series:

6 , 14 , 21 , ?? , 35 , 42

Ans.28 i.e.(6*4+4)=28

6*2+2=14 , 6*3+3=21 , 6*4+4=28 , 6*5+5=35 , 6*6+6=42.
Logic: 1st number *2 + 2 = second, 1st number * 3 + 3 = third, 1st number * 4 + 4 = fourth and so on.

Q16. A car crosses a 1200 m long road in 2 minutes. What will be it’s speed in km per hour?

A. 11.88

B. 18.0

C. 21.6

D. 36.0

Answer: 36.0 km/h i.e. [(1200/1000) / (2/60)]

Logic: Converting 1200 to kilometer by dividing it by 1000 and converting 2 to hour by dividing it by 60 and dividing both.

Q17. Next number in the series is:

18, 21 , 19, 22, 20, ??

Ans: 23 i.e. 20 + 3 = 23
18, 18 + 3 = 21, 21 – 2 =19 and so on i.e. +3 and then -2 in alternate numbers.
Logic: This is a simple alternating addition and subtraction series. In the first pattern, 3 is added; in the second, 2 is subtracted and so on.