# Number Series Questions for IBPS PO Exams

## Number Series Questions with Solution

Directions (Q.1 – Q.10): In each of the following series only one no is wrong. Find out that wrong number.
Q.1        6      9.5       20       51.5        155         550.25
a). 9.5
b). 550.25
c). 20
d). 155
e).None of these

Q.2       18        19        27        54       117        243
a). 19
b). 27
c). 243
d). 117
e). None of these.

Q3.      14       28        80       576        8960        285696
a). 28
b). 14
c). 576
d). 285696
e) None of these.

Q4.       44     22       62      33        99       44.5         133.5
a). 44
b). 62
c). 133.5
d) 99
e) None of these.

Q.5    7      14     37         77      157         317
a). 37
b). 157
c). 317
d). 14
e) None of these.

Q.6    7         7      13       39       97         217
a). 13
b). 97
c). 39
d). 217
e) None of these.

Q.7      2       9       30      105      420       2195       13182
a).9
b). 420
c).105
d). 13182
e) None of these.

Q.8.    10       19       57        223       1111        6671
a). 19
b). 1111
c). 57
d). 6671
e). None of these.

Q.9.    36       18         27        81        236.25         1063.125
a).81
b). 36
c).236.25
d). 1063.125
e). None of these.

Q.10      800       400       160         64       32        16
a).400
b). 32
c).64
d).16
e) none of these

Directions: (Q 11 – Q 15). What should come in place of question mark (?) in the following series.
Q.11        13       22          57          212           1035          ?
a). 4170
b). 5075
c). 6174
d).6205
e) None of these.

Q.12.      5         6         14        41        105         ?
a).215
b). 315
c).230
d) 340
e) None of these.

Q.13.   123       173        231      297       371        453        ?
a).540
b). 543
c).580
d). 510
e). None of these

Q.14.    9         18       ?            92       173         294
a). 32
b). 43
c). 27
d). 18
e) None of these

Q.15.     1378      687       340.5        ?         78.125           30.0625
a).166.25
b). 186.25
c). 178.25
d). can’t be determined
e) None of these
Solution

Ans.1 –d.
2nd term = (1st term * 1.5 + 0.5)
3rd term =(2nd term * 2 + 1)
4th term = (3rd term * 2.5 + 1.5) and so on.

Ans.2 – d
2nd term = (1st term + 13)
3rd term = (2nd term + 23)
4th term = (3rd term + 33)
5th term = ( 4th term + 43) and so on,
Hence 117 is wrong.

Ans.3 – a
2nd term = (1st term * 2 – 22)
3rd term =(2nd term * 4 – 42)
4th term = (3rd term * 8 – 82)
5th term = (4th term * 16 – 256)
6th term = (5th term * 32 – 1024)
Hence 28 is wrong.

Ans.4 –b
44 /2= 22
22 * 3 =66
66/2=33
33*3=99
99/2=44.5
44.5*3=133.5

Ans.5 – d
The series is *2 + 3, *2 + 3, ....
Hence 14 is wrong ans.

Ans.6 – c
1st term + 13 – 1 = 7
7 + 23 -2=13
13 + 33 -3=37
37 + 43-4=97
97 + 53-5=217

Ans.7 – b
The series goes as follows
2 * 1 + 7 * 1 =9
9 * 2 + 6 * 2=30
30 * 3 + 5 * 3 = 105
105 * 4 + 4 * 4=436
436 * 5+ 3 * 5=2195
2195 * 6 + 2 * 6=13182

Ans.8 – d
The series is x2 + 1, x3 -2, x4 + 3,....

Ans.9 – a).
The series is x0.5, x1.5, x 2.5, x3.5, ....

Ans.10 – c.
800/2=400
400* 2/5=160
160/2=80
80*2/5=32
32/2=16

Ans.11 –d.
1st term * 2 – 22
2nd term * 3 - 32
3rd term * 4 - 42
4th term * 5 - 52
And so on.

Ans.12 –d
02 + 5 = 5
12 + 5= 6
32 + 5= 14
62 + 5 = 11
102 + 5=105
152+ 5=230

Ans.13 –b
123 + 50=173
173+58=231
231+66=297
297+74=371
371+82=453
453+90=543

Ans.14 –b.
2nd term = 1st term + 12
3rd term = 2nd term + 33
4th term = 3rd term + 52
5th term = 4th term + 72 and so on.

Ans. 15 – a.
2nd term = 1378/2 – 2=687
3rd term = 687/2 -3=340.5
4th term = 340.5/2 – 4=166.25
5th term = 166.25/2 -5=78.125
6th term = 78.125/2 -6=30.0625 