# Number Series - 1

Directions (Q.1-5): What should come in place of question mark (?) in the following number series questions?

1. 2 1 1 1.5 3 ?

Ans: 7.5

Explanation: 2 × 0.5 = 1

1 × 1 = 1

1 × 1.5 = 1.5

1.5 × 2 = 3

3 × 2.5 = 7.5

2. 51 66 83 102 123 ?

Ans: 146

Explanation: 72 + 2 = 51

82 + 2 = 66

92 + 2 = 83

102 + 2 = 102

112 + 2 = 123

122 + 2 = 146

3. 4 24 84 264 804 ?

Ans: 2424

Explanation: 4 × 3 + 12 = 24

24 × 3 + 12 = 84

84 × 3 + 12 = 264

264 × 3 + 12 = 804

804 × 3 + 12 = 2424

4. 24 36.2 30.4 33.6 32 ?

Ans: 32.8

Explanation: 24 + 12.8 = 36.8

36.8 − 6.4 = 30.4

30.4 + 3.2 = 33.6

33.6 − 1.6 = 32

32 + 0.8 = 32.8

5. 6 9 13.5 20.25 30.375 ?

Ans: 49.7525

Explanation: 6 × 3 ÷ 2 = 9

9 × 3 ÷ 2 = 13.5

13.5 × 3 ÷ 2 = 20.25

20.25 × 3 ÷ 2 = 30.375

30.375 × 3 ÷ 2 = 45.5625

Directions (Q.6-10): In each of the following questions, a number series is given. One number is missing. What is that missing number?

6. 2 ? 19 45 99 209 431

Ans: 7

Explanation: 2 × 2 + 3 = 7

7 × 2 + 5 = 19

19 × 2 + 7 = 45

45 × 2 + 9 = 99

99 × 2 + 11 = 209

209 × 2 + 13 = 431

7. ?   4   6   12   30   90   315

Ans: 4

Explanation: 4 × 1 = 4

4 × 1.5 = 6

6 × 2 = 12

12 × 2.5 = 30

30 × 3 = 90

90 × 3.5 = 315

8. 48   62   78   96   116   ?   162

Ans: 138

Explanation: 72 − 1, 82 − 2, 92 − 3,

102 − 4, 112 − 5,

122 − 6, 132 − 7

9. 54   35   ?   3   −10   −21   −30

Ans: 18

Explanation: 54 − 19 = 35

35 − 17 = 18

18 − 15 = 3

3 − 13 = −10

−10 − 11 = −21

− 21 − 9 = −30

10. 11   12   20   43   ?   339.5   1194.25

Ans: 111.5

Explanation: 11 × 1 + 1 = 12

12 × 1.5 + 2 = 20

20 × 2 + 3 = 43

43 × 2.5 + 4 = 111.5

111.5 × 3 + 5 = 339.5

339.5 × 3.5 + 6 = 1194.25

Directions (Q.11-15): In each of the following number series questions a number is wrong. You have to identify that number.

11. 4   6   9   13.5   20   30.375

Ans: 20

Explanation: 4 × 1.5 = 6

6 × 1.5 = 9

9 × 1.5 = 13.5

13.5 × 1.5 = 20.25

20.25 × 1.5 = 30.375

12. 11   13   30   99   412   2085

Ans: 11

Explanation: 12 × 1 + 1 = 13

13 × 2 + 4 = 30

30 × 3 + 9 = 99

99 × 4 + 16 = 412

412 × 5 + 25 = 2085

13. 3   4   10   32   155   924

Ans: 10

Explanation: 3 × 2 − 2 = 4

4 × 3 − 3 = 9

9 × 4 − 4 = 32

32 × 5 − 5 = 155

155 × 6 − 6 = 924

14. 208   214   232   262   302   358

Ans: 302

Explanation: 208 + 6 = 214

214 + 18 = 232

232 + 30 = 262

262 + 42 = 304

304 + 54 = 358

15. 156   170   192   226   280   364

Ans: 364

Explanation: 156 + 14 = 170

170 + 14 + 8 = 192

192 + 22 + 12 = 226

226 + 34 + 20 = 280

280 + 54 + 32 = 366

Directions(Q.16-20): In each of the following questions a number series is given. After theseries, a number is given followed by (a), (b), (c), (d) and (e). You have to complete theseries starting with the number given, following the sequence of the original series and answer the questions that follow the series.

16. 3   732   1244   1587   1803   1928

5    (a)      (b)      (c)       (d)       (e)

What will come in place of (d)?

Ans: 1805

Explanation: The difference between the numbers are perfect cubes ... required number in (d) position is 1805

17. 16   4     2   1.5   1.5   1.875

4    (a)  (b) (c)    (d)     (e)

What will come in place of (b)?

Ans: 0.5

Explanation: 16 × 0.25 = 4

4 × 0.5 = 2

2 × 0.75 = 1.5

1.5 × 1 = 1.5

1.5 × 1.25 = 1.875

Required number is

4 × 0.25 = 1

1 × 0.5 = 0.5

18. 3   19   99   499   2499   12499

2   (a)   (b)    (c)     (d)        (e)

What will come in place of (c)?

Ans: 374

Explanation: 3 × 5 + 4 = 19

19 × 5 + 4 = 99

99 × 5 + 4 = 499

499 × 5 + 4 = 2499

2499 × 5 + 4 = 12499

Required number is

2 × 5 + 4 = 14

14 × 5 + 4 = 74

74 × 5 + 4 = 374

19. 14   19   12   23   10   27

11  (a)   (b)  (c)   (d)  (e)

What will come in place of (b)?

Ans: 9

Explanation: 14 + 5 = 19

19 − 7 = 12

12 + 11 = 23

23 − 13 = 10

10 + 17 = 27

Required number is

11 + 5 = 16

16 − 7 = 9

Short cut: Vertical difference is always constant

20. 24   144   180   900   925   3700

17    (a)     (b)     (c)      (d)     (e)

What will come in place of (e)?

Ans: 2860

Explanation: 24 × 6 = 144

144 + 62 = 180

180 × 5 = 900

900 + 52 = 925

925 × 4 = 3700

Required number is

17 × 6 = 102

102 + 36 = 138

138 × 5 = 690

690 + 25 = 715

715 × 4 = 2860

Directions (Q.21-25): In each of the following questions, a number is wrong. You have to identify that number.

21. 7.2   32   156   776   3876   19276

Ans: 19276

Explanation: 7.2 × 5 − 4 = 32

32 × 5 − 4 = 156

156 × 5 − 4 = 776

776 × 5 − 4 = 3876

3876 × 5 − 4 = 19376

22. 328   340   360   412   508   700

Ans: 360

Explanation: 328 + 12 = 340

340 + 24 = 364

364 + 48 = 412

412 + 96 = 508

508 + 192 = 700

23. 12   18   45   156.5   708.75   3898.125

Ans: 156.5

Explanation: 12 × 1.5 = 18

18 × 2.5 = 45

45 × 3.5 = 157.5

157.5 × 4.5 = 708.75

708.75 × 5.5 = 3898.125

24. 0.7   1.1   1.9   3.1   4.7   6.9

Ans: 6.9

Explanation: 0.7 + 0.4 = 1.1

1.1 + 0.8 = 1.9

1.9 + 1.2 = 3.1

3.1 + 1.6 = 4.7

4.7 + 2 = 6.7

25. 3399   1131   375   125   39   11

Ans: 125

Explanation: 3399 ÷ 3 − 2 = 1131

1131 ÷ 3 − 2 = 375

375 ÷ 3 − 2 = 123

123 ÷ 3 − 2 = 39

39 ÷ 3 − 2 = 11

Posted Date : 31-03-2023

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