# Number Series questions for SBI Clerk exam

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Number series reasoning questions for SBI Clerk. SBI Po and Clerk banking questions on number series. Questions from previous asked banking question papers are given below.

## Number Series for SBI Clerk:

For more questions visit SBI Clerk Previous question papers (solved)

Instructions (1 – 5):
What should come in place of question mark (?) in the following numbers series

Question 1: 12, 6.5, 7.5, 12.75, 27.5, 71.25, ?

a) 225.75
b) 216.75
c) 209.75
d) 236.75
e) 249.75

Question 2: 16, 24, 36, 54, 81, 121.5 ?

a) 182.25
b) 174.85
c) 190.65
d) 166.55
e) 158.95

Question 3: 12, 12, 18, 45, 180, 1170, ?

a) 13485
b) 14675
c) 15890
d) 16756
e) 12285

Question 4: 22, 23, 27, 36, 52, 77, ?

a) 111
b) 109
c) 113
d) 117
e) 115

Question 5: 16, 14, 24, 66, 256, 1270, ?

a) 8564
b) 5672
c) 4561
d) 7608
e) 6340

Instructions (6 – 10):
Find the wrong number in given series sequence.

Question 6: 1, 4, 15, 64 325, 1955

a) 15
b) 64
c) 325
d) 1955
e) None of these

Question 7: 6, 12, 21, 33, 49, 66

a) 21
b) 33
c) 49
d) 66
e) None of these

Question 8: 6, 11.5, 19, 28.5, 41

a) 6
b) 11.5
c) 41
d) 28.5
e) None of these

Question 9: 5, 26, 82, 214, 401, 702

a) 26
b) 82
c) 214
d) 401
e) None of these

Question 10: 5,20,73,274,1049

a) 20
b) 73
c) 274
d) 1049
e) None of these

Solutions for Number Series Questions for SBI Clerk:

Solutions:

The given series is based on the following sequence,
(12+1)*0.5 = 6.5
(6.5+1)*1 = 7.5
(7.5+1.5)*1.5=12.75
(12.75+1)*2 = 27.5
(27.5+1)*2.5 = 71.25
(71.25+1)*3 = 216.75

Each number in the series is 1.5 times the preceding number.
Hence, 16*1.5 = 24
24*1.5 = 36
36*1.5 = 54
54*1.5=81
81*1.5 = 121.5
So, the next number is 121.5*1.5 = 182.25

The ratio between preceding terms of the sequence are in a fibonacci sequence.
For example, 12/12 = 1
18/12 = 1.5
45/18 = 2.5 (which is 1+1.5)
180/45 = 4 (which is 1.5+2.5)
1170/180 = 6.5 (which is 2.5+4)
Hence, the next ratio would be 4+6.5=10.5
And the required number is 1170*10.5 = 12285

The difference between consecutive terms of the series is a perfect square.
For example,
23-22 = 1
27-23 = 4
36-27 = 9
52-36 = 16
77-52 = 25
Hence, the next difference between the numbers will be 36 and the required number is 77+36 = 113

The given terms are in the following series,
14 = 16*1 – 2*1
24 = 14*2 – 2*2
66 = 24*3 – 2*3
256 = 66*4 – 2*4
1270 = 66*5 – 2*5
Hence, the next term equals 1270*6 – 2*6 = 7608

4 = 1*2+2 ; 15 = 4*3+3 ; 64 = 15*4+4 ; 325 = 64*5+5 ; 1956 = 325*6+6
The nth term is of the form,
$$T_n=(T_{n-1}\times n)+n$$
The last term does not follow the pattern and is thus the wrong number in the sequence.

2*2+2 = 6 ; 3*3+3 = 12 ; 4*4 + 5= 21 ; 5*5 +8 = 33 ; 6*6 + 12 = 48

1.5*2 + 3 = 6
2.5*3 + 4 = 11.5
3.5*4 + 5 = 19
4.5*5 + 6 = 28.5
5.5*6 + 7 = 40