# Logical reasoning -Number series - CSEET

1. At this series: 12, 11, 13, 12, 14, 13, … What number should come next?

A. 10

B. 16

C. 13

D. 15

Answer: Option D.

Explanation : This is an alternating number of subtraction series. First, 1 is subtracted, then 2 is added.

2. At this series: 36, 34, 30, 28, 24, … What number should come next?

A. 22

B. 26

C. 23

D. 20

Answer: Option A.

Explanation : This is an alternating number of subtraction series. First, 2 is subtracted, then 4, then 2, and so on.

3. At this series: 7, 10, 8, 11, 9, 12, … What number should come next?

A. 7

B. 12

C. 10

D. 13

Answer: Option C.

Explanation : Its an alternating addition and subtraction series. 3 is added in the first pattern, and then 2 is subtracted.

4. From the give series: 2, 1, (1/2), (1/4), … What number should come next?

A. (1/3)

B. (1/8)

C. (2/8)

D. (1/16)

Answer: Option B.

Explanation : It’s a division series. Every number is half of the previous number. The number is divided by 2 successively to get the next result. 4/2 = 2. 2/2 = 1. 1/2 = ½. (1/2)/2 = ¼. (1/4)/2 = 1/8 and so on.

5. Watch this series: 80, 10, 70, 15, 60, … What number should come next?

A. 20

B. 25

C. 30

D. 50

Answer: Option A.

Explanation : This is an alternating addition and subtraction series. In the first pattern, 10 is subtracted from each number to arrive at the next. In the second, 5 is added to each number to arrive at the next.

6. Look at this series: 36, 45, 24, 32, 12, ... What number should come next?

A. 29

B. 39

C. 32

D. 19

Answer – D

Explanation : Subtraction series

7. Look at this series: 22, 21, 23, 22, 24, 23, ... What number should come next?

A. 22

B. 24

C. 25

D. 26

Answer: Option C

Explanation: In this simple alternating subtraction and addition series; 1 is subtracted, then 2 is added, and so on.

8. Look at this series: 53, 53, 40, 40, 27, 27, ... What number should come next?

A. 12

B. 14

C. 27

D. 53

Answer: Option B Explanation:

In this series, each number is repeated, then 13 is subtracted to arrive at the next number.

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

9. 42 40 38 35 33 31 28

A. 25 22

B. 26 23

C. 26 24

D. 25 23

E. 26 22

Answer: Option C

Explanation: This is an alternating subtraction series in which 2 is subtracted twice, then 3 is subtracted once, then 2 is subtracted twice, and so on.

10. 6 10 14 18 22 26 30

A. 36 40

B. 33 37

C. 38 42

D. 34 36

E. 34 38

Answer: Option E

Explanation: This simple addition series adds 4 to each number to arrive at the next.

11. 8 12 9 13 10 14 11

A. 14 11

B. 15 12

C. 8 15

D. 15 19

E. 8 5

Answer: Option B

Explanation: This is an alternating addition and subtraction series, in which the addition of 4 is alternated with the subtraction of 3.

12. 36 31 29 24 22 17 15

A. 13 11

B. 10 5

C. 13 8

D. 12 7

E. 10 8

Answer: Option E

Explanation: This is an alternating subtraction series, which subtracts 5, then 2, then 5, and so on.

13. 3 5 35 10 12 35 17

A. 22 35

B. 35 19

C. 19 35

D. 19 24

E. 22 24

Answer: Option C

Explanation: This is an alternating addition series, with a random number, 35, interpolated as every third number. The pattern of addition is to add 2, add 5, add 2, and so on. The number 35 comes after each "add 2" step.

14. In these questions, a number series is given. Find out the missing number.

6 15 48 171 ? 3645

A. 716

B. 736

C. 746

D. 720

E. None of these

Answer – D. 720

Explanation :

(6 * 1) + (1 * 9) = 15

(15 * 2) + (2 * 9)= 48

(48 * 3) + (3 * 9)= 171

(171 * 4) + (4 * 9) = 720

(720 * 5) + (5 * 9) = 3645

15. 5 3 4 ? 17 45

A. 7.5

B. 4.5

C. 6.5

D. 8.5

E. None of these

Answer – A. 7.5

Explanation :

5 * 0.5 + 0.5 = 3

3 * 1 + 1 = 4

4 * 1.5 + 1.5 = 7.5

7.5 * 2 + 2 = 17

17 * 2.5 + 2.5 = 45

16. 4 11 36 103 ? 939

A. 345

B. 316

C. 375

D. 355

E. None of these

Answer – B. 316

Explanation :

4 * 3 – 1 = 11

11 * 3 + 3 = 36

36 * 3 – 5 = 103

103 * 3 + 7 = 316

316 * 3 – 9 = 939

17. 6 13 41 ? 216 391

A. 123

B. 104

C. 153

D. 113

E. None of these

Answer – B. 104

Explanation :

6 + 7 * 1² = 13

13 + 7 * 2² = 41

41 + 7 * 3² = 104…..

18. 715 524 333 ? 119 68

A. 224

B. 232

C. 242

D. 252

E. None of these

Answer – A. 224

Explanation :

9³ – 14 = 715

8³ + 12 = 524

7³ – 10 = 333……

19. 58 60 116 354 1408 ?

A. 6050

B. 7050

C. 7080

D. 6070

E. None of these

Answer – B. 7050

Explanation :

58 * 1 + 2 = 60

60 * 2 – 4 = 116

116 * 3 + 6 = 354

354 * 4 – 8 = 1408…..

20. 14, 78, 252, 620, ?, 2394

A. 1340

B. 1290

C. 1470

D. 1860

E. None of these

Answer – B. 1290

Explanation :

2^4 – 2, 3^4 – 3, 4^4 – 4, 5^4 – 5…

21. 3 5 15 38 ? 464 2422

A. 240

B. 420

C. 150

D. 120

E. None of these

Answer – D. 120

Explanation :

(5 * 1) + 10 = 15

(15 * 2 ) + 8 = 38

(38 * 3) + 6 = 120

(120 * 4) + 4 = 484

(484 * 5) + 2 = 2422

22. 8 18 51 208 1035 ?

A. 6776

B. 6263

C. 6463

D. 6216

E. None of these

Answer – D. 6216

Explanation :

8 * 2 + 2 = 18

18 * 3 – 3 = 51

51 * 4 + 4 = 208

208 * 5 – 5 = 1035….

23. 24 11 9 14 48 ?

A. 368

B. 334

C. 364

D. 324

E. None of these

Answer – A. 368

Explanation :

24 * 0.5 – 1 = 11

11 * 1 – 2 = 9

9 * 2 – 4 = 14

14 * 4 – 8 = 48

24. 3 2 2 5 5 5 7 8 8 9 11 11 ?

1. 12

2. 11

3. 9

4. 14

5. 16

Answer: Option 2

Explanation: There are three parallel series going on in this question. The 1st, 4th, 7th terms are using logic of -1, 2nd, 5th and 8th terms are using logic of +1 and 3rd, 6th and 9th terms are using logic of +1 again. Answer will be 11, which belongs to 1st, 4th and 7th term.

25. 7 9 8 6 10 9 5 11 10 ? 12

1. 4

2. 11

3. 56

4. 5

5. 29

Answer: Option 1

Explanation: There are three parallel series going on in this question. The 1st, 4th, 7th terms are using logic of -1, 2nd, 5th and 8th terms are using logic of +1 and 3rd, 6th and 9th terms are using logic of +1 again. Answer will be 4, which belongs to 1st, 4th and 7th term.