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
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
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