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

1. -1, 5, 23, 59, 119, ?

Ans: 5
The pattern is, (13 – 2) = -1, (23 – 3) = 5, (33 – 4) = 23, (43 – 5) = 59, (53 – 6) = 119, (63 – 7) = 209

 

2. 48, 64, 82, 102, ?, 148

Ans: 4
The pattern is 9×5+3=48, 10×6+4=64, 11×7+5=82, 12×8+6=102, 13×9+7=124, 14×10+8=148

 

3. 28, 77, 158, ?, 448, 673

Ans: 1
The pattern is 28+72=77, 77+92=158, 158+112=279, 279+132=448, 448+152=673

 

4. 14, 42, 168, 840, ?, 35280

Ans: 4
14×3=42, 42×4=168, 168×5=840, 840×6=5040, 5040×7=35280

 

5. 2, 5, 17, 71, 359, ?

Ans: 2
The pattern is
(2 X 2) + 1 = 5, (5 X 3) + 2 = 17, (17 X 4) + 3 = 71, (71 X 5) + 4 = 359, (359 X 6) + 5 = 2159

 

Directions:(6-10) Find the wrong term in the series given below.

6. 11, 18, 27, 40, 51

Ans: 4
The pattern is as follows:
2 x 3 + 5 = 11
3 x 4 + 6 = 18
4 x 5 + 7 = 27
5 x 6 + 8 = 38
6 x 7 + 9 = 51

 

7. 145, 121, 93, 79, 61, 45

Ans: 5
The pattern is as follows:
122 + 1 = 145
112 + 0 = 121
102 + -1 = 99
92 + -2 = 79
82 + -3 = 61
72 + -4 = 45

 

8. 2, 29, 83, 156, 272, 407

Ans: 1
The pattern is as follows:
2 + 27 x 1 = 29
29 + 27 x 2 = 83
83 + 27 x 3 = 164
164 + 27 x 4 = 272
272 + 27 x 5 = 407

 

9. 40, 60, 100, 160, 220, 260

Ans: 5
The pattern is 20 being multipled by consecutive prime numbers:
20 x 2 = 40
20 x 3 = 60
20 x 5 = 100
20 x 7 = 140
20 x 11 = 220
20 x 13 = 260

 

10. 508, 338, 210, 118, 50, 18

Ans: 1
The pattern is as follows:
83 – 4 = 508
73 – 5 = 338
63 – 6 = 210
53 – 7 = 118
43 – 8 = 56
33 – 9 = 18

 

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13 thoughts on “Number Series”

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