# Number Series Questions For IBPS RRB PO

Download Top-20 IBPS RRB PO Number Series Questions PDF. Number Series questions based on asked questions in previous year exam papers very important for the IBPS RRB PO (Officer Scale-I, II & III) exam.

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**Instructions**

One of the numbers in the given series is incorrect. Find the incorrect number in the series

**Question 1:Â **7, 33, 137, 553, 2217, 8871

a)Â 33

b)Â 137

c)Â 553

d)Â 8871

e)Â 2217

**Question 2:Â **6, 12, 15, 30, 42, 56

a)Â 12

b)Â 30

c)Â 6

d)Â 56

e)Â 15

**Question 3:Â **6, 19, 58, 172, 526

a)Â 172

b)Â 58

c)Â 19

d)Â 526

e)Â 6

**Question 4:Â **6,36,180,720,2160,4230

a)Â 6

b)Â 4230

c)Â 2160

d)Â 36

e)Â 720

**Instructions**

Which of the following numbers doesn’t fit the below series

**Question 5:Â **343, 512, 729, 1000, 1329

a)Â 1000

b)Â 512

c)Â 343

d)Â 1329

e)Â 729

**Question 6:Â **1, 9, 23, 49, 81, 121

a)Â 9

b)Â 23

c)Â 1

d)Â 121

e)Â 81

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**Question 7:Â **51, 54, 59, 67, 75, 86

a)Â 51

b)Â 75

c)Â 67

d)Â 59

e)Â 86

**Question 8:Â **21, 22, 26, 35, 51, 74

a)Â 74

b)Â 22

c)Â 35

d)Â 51

e)Â 21

**Question 9:Â **1, 36, 121, 256, 484, 676

a)Â 36

b)Â 121

c)Â 1

d)Â 484

e)Â 676

**Instructions**

Which of the following numbers doesn’t fit in the below series?

**Question 10:Â **784, 392, 400, 200, 208, 102

a)Â 392

b)Â 400

c)Â 208

d)Â 200

e)Â 102

**Question 11:Â **3, 4, 10, 45, 196, 1005

a)Â 4

b)Â 45

c)Â 1005

d)Â 10

e)Â 196

**Question 12:Â **11, 16, 31, 56, 93, 136, 191

a)Â 16

b)Â 93

c)Â 136

d)Â 31

e)Â 11

**Question 13:Â **5, 8, 13, 15, 29, 40

a)Â 8

b)Â 13

c)Â 29

d)Â 40

e)Â 15

**Question 14:Â **2, 4, 16, 96, 768, 7860

a)Â 4

b)Â 7860

c)Â 768

d)Â 16

e)Â 96

**Instructions**

Which of the following number doesn’t fit in the below series

**Question 15:Â **835, 819, 799, 781, 759, 735

a)Â 799

b)Â 835

c)Â 735

d)Â 781

e)Â 759

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**Question 16:Â **3, 24, 81, 192, 373

a)Â 81

b)Â 24

c)Â 192

d)Â 3

e)Â 373

**Question 17:Â **198, 200, 200, 197, 202, 196

a)Â 200

b)Â 198

c)Â 202

d)Â 196

e)Â 197

**Question 18:Â **200, 219, 255, 314, 390

a)Â 219

b)Â 200

c)Â 255

d)Â 314

e)Â 390

**Question 19:Â **26, 37, 50, 65, 82, 102

a)Â 102

b)Â 37

c)Â 26

d)Â 50

e)Â 82

**Instructions**

Which of the following number doesn’t fit in the given series?

**Question 20:Â **19, 38, 114, 228, 682

a)Â 38

b)Â 114

c)Â 19

d)Â 682

e)Â 228

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**Answers & Solutions:**

**1)Â AnswerÂ (D)**

7*4+5 = 28+5 = 33

33*4+5 = 132+5 = 137

137*4+5 = 548+5 = 553

553*4+5 = 2212+5 = 2217

2217*4+5 = 8868+5 = 8873

Hence, 8871 must be replaced by 8873

**2)Â AnswerÂ (E)**

2*3 = 6

3*4 = 12

Next term would be 4*5 = 20

5*6 = 30

6*7 = 42

7*8 = 56

Hence, 15 must be replaced by 20.

**3)Â AnswerÂ (A)**

The pattern being followed here is *3+1

6*3+1 = 19,

19*3+1=58,

so next term would be 58*3+1= 175

175*3+1 = 526.

Hence, 172 must be replaced by 175.

**4)Â AnswerÂ (B)**

36 = 6*6

180 = 36*5

720 = 180*4

2160 = 720*3

So the next term will be, 2160*2 = 4320

Hence, 4230 must be replaced by 4320.

**5)Â AnswerÂ (D)**

$343 = 7^3$

$512 = 8^3$

$729 = 9^3$

$1000 = 10^3$

Here, all numbers are cubes of 7,8,9,10,11,…

Hence, Next number should be $1331 = 11^3$

Hence, 1329 should be replaced by 1331.

**6)Â AnswerÂ (B)**

$1 = 1^2$

$9 = 3^2$

$25 = 5^2$

$49 = 7^2$

$81 = 9^2$

$121 = 11^2$

Here, Numbers are squares of odd numbers.

Hence, 23 should be replaced by 25.

**7)Â AnswerÂ (C)**

51+3 = 54

54+5 = 59

59+8 = 67

67+8 = 75

75+11 = 86

Here, Difference between the numbers are odd numbers.

Hence, 67 should be replaced by 66.

**8)Â AnswerÂ (A)**

21+1 = 22

22+4 = 26

26+9 = 35

35+16 = 51

51+25 = 76

Hence, 74 should be replaced by 76.

**9)Â AnswerÂ (D)**

$1 = 1^1$

$36 = 6^2$

$121 = 11^2$

$256 = 16^2$

$484 = 22^2$

$676 = 26^2$

Here, Numbers are the squares of 1, 6, 11, 16, 22, 26,…

Difference between these numbers is 5 in all numbers except 16,22,26

Hence, 22 should be replaced by 21 and therefore 484 should be replaced by 441.

**10)Â AnswerÂ (E)**

784/2 = 392

400/2 = 200

208/2 = 104.

Hence, 102 should be replaced by 104.

**11)Â AnswerÂ (D)**

The given series is as below

3*1+1 = 3+1 = 4

4*2+4 = 8+4 = 12

12*3+9 = 36+9 = 45

45*4+16 = 180+16 = 196

196*5+25 = 980+25 = 1005

Hence, 12 should be replaced by 10.

**12)Â AnswerÂ (B)**

11+5 = 16

16+15 = 31

31+25 = 56

56+37 = 93

93+43 = 136

136+55 = 191.

Here, Difference between the numbers are 5, 15, 25, 35, …..

Hence, After 56, it should be

56+35 = 91.

Hence, 93 should be replaced by 91.

**13)Â AnswerÂ (E)**

5+3 = 8

8+5 = 13

13+2 = 15

15+14 = 29

29+11 = 40

Here, The difference are odd numbers.

Hence, After 13, it should be

13+7 = 20

20+9 = 29.

Hence, 15 should be replaced by 20.

**14)Â AnswerÂ (B)**

2*2 = 4

4*4 = 16

16*6 = 96

96*8 = 768

768*10 = 7680

Hence, 7860 should be replaced by 7680.

**15)Â AnswerÂ (A)**

Difference in series is in increasing order as 16,18,20,22,24,….

835-16 = 819

819-18 = 801

801-20 = 781

781-22 = 759

759-24 = 735

Hence, 799 should be replaced by 801.

**16)Â AnswerÂ (E)**

$3\times1^3 = 3$

$3\times2^3 = 3\times8 = 24$

$3\times3^3 = 3\times27 = 81$

$3\times4^3 = 3\times64 = 192$

$3\times5^3 = 3\times125 = 375$

Hence, 373 must be replaced by 375.

**17)Â AnswerÂ (D)**

The given series is a combination of two series.

198, 200, 202, …

200, 197, 196,….

In the first series,

198+2 = 200

200+2 = 202

In the second series,

200-3 = 197

197-3 = 194

Hence, 196 must be replaced by 194.

**18)Â AnswerÂ (C)**

The given series is in the form of

200+19 = 219

219+38 = 257

257+57 = 314

314+76 = 390

Hence, 255 should be replaced by 257.

**19)Â AnswerÂ (A)**

26+11 = 37

37+13 = 50

50+15 = 65

65+17 = 82

82+19 = 101

Hence, 102 should be replaced by 101.

**20)Â AnswerÂ (D)**

19*2 = 38

38*3 = 114

114*2 = 228

228*3 = 684

Hence, 682 must be replaced by 684.