This is one of the most important topic for SSC, Railways and as well as for banking examinations. Here, mostly questions will be asked on some standard logic.
* Square, Square root
* Cube, Cube root
* Sum, Difference
* Product, Division
* Double difference
* Fractions
* Binomial series
* Decreasing / Increasing series
1. 10, 12, 18, 42, 162, ?
A) 216 B) 416 C) 325 D) 882
Sol: Here, in the given series, all the numbers are some what close to each other. whenever all the numbers are close, the first logic we should check is difference.
If we observe the differences
they are like 2! = 2, 3! = 6, 4! = 24 and 5! = 120, so the next difference must be,
6 factorial = 6! = 720
next number = 162 + 720 = 882
Ans: D
2. 2, 8, 28, 102, 432, ?
A) 600 B) 1820 C) 2190 D) 2560
Sol: If we observe, here the first and last numbers are somewhere far away, so more chance is there for multiplication logic.
432 × 5 + 30 = 2190
Ans: C
3. 0, 1, 8, 54, 384, ?
A) 620 B) 2560 C) 3000 D) 3200
Sol: Here the logic is
0! × 0 2 = 0
1! × 1 2 = 1
2! × 2 2 = 8
3! × 3 2 = 54
4! × 4 2 = 384
the next number is 5! × 5 2 = 3000
Ans: C
4. 8, 3, 0, −1, 0, ?
A) 0 B) 1 C) 2 D) 3
Sol: Here, as the numbers are close to each other, we can go with the difference logic.
Required number = 3 − 0 = 3
Ans: D
5. 26, 34, ?, 50, −6, 66
A) 25 B) 10 C) 16 D) 15
Sol: It is like increasing, decreasing series and all the numbers are close to each other, so addition and subtraction logic.
26 + (+ 8) = 34
34 + (− 24) = 10
10 + (+ 40) = 50
Odd multiple of 8
50 + (− 56) = − 6
− 6 + (+ 72) = 66
Ans: B
6. 196, 194, 198, 190, ?
A) 196 B) 200 C) 204 D) 206
Sol: It is also increasing / decreasing series
⇒ 190 + 16 = 206
Ans: D
7. 32, ?, 1024, 2048, 2048
A) 128 B) 256 C) 512 D) 24
Sol: Here, the first number and last numbers are some where for away. so, it must be based on multiplication logic.
32 × 8 = 256
256 × 4 = 1024
1024 × 2 = 2048
2048 × 1 = 2048
Ans: B
8. 8, 4, 4, 8, 32, ?
A) 16 B) 64 C) 128 D) 256
Sol: It is a kind of decreasing and there after continuously increasing series. so, first number must be multiplied by a number which is less then one.
8 × 0.5 = 4
4 × 1 = 4
4 × 2 = 8
8 × 4 = 32
32 × 8 = 256
Ans: D
9. 15, 5, 4.5, 5.8, 7.9, ?
A) 9.25 B) 10.74 C) 6.25 D) 8.56
Sol: If we observe, this series is in decreasing manner in the starting and there after increasing.
15 × 0.2 + 2 = 5
5 × 0.3 + 3 =4.5
4.5 × 0.4 + 4 = 5.8
5.8 × 0.5 + 5 = 7.9
7.9 × 0.6 + 0.6 = 10.74
Ans: B
10. 96, 320, 800, 1600, ?
A) 1000 B) 1200 C) 2666.7 D) 3201.6
Sol: Here the logic is
Ans: C
11. 110, ?, 42, 20, 6
A) 72 B) 80 C) 65 D) 50
Sol: If we observe the series, all the numbers are close to square numbers
112 − 11 = 110
92 − 9 = 72
72 − 7 = 42
52 − 5 = 20
32 − 3 = 6
Ans: A
Sol: This series is having mixed fractions and numbers are close to each other. First convent the mixed fractions into improper fractions.
Ans: C
13. 9, 15, 24, 39, 63, ?
A) 85 B) 91 C) 99 D) 105
Sol: Here as all the numbers are close to each other, we can go with the difference logic.
next number = 63 + 36 = 99
Ans: C
14. 18900, 4200, 1200, 480, ?
A) 360 B) 320 C) 240 D) 120
Sol: Here, after observing the first and last terms, it is clear that the series is based on division logic
Ans: B
15. 17, 19, 28, 92, ?
A) 126 B) 257 C) 625 D) 717
Sol: Here, as all the numbers are close to each other.
We can go with the differce logic.
⇒ next number = 92 + 625 = 717
Ans: D
16. 71, 88, 113, 150, 203, ?
A) 300 B) 276 C) 216 D) 285
Sol: If we observe this series, all the numbers are close ti each other. So, the series must be based on difference logic
⇒ Next number = 203 + 73 = 276
Ans: B
17. 3, 5, 17, 97, 769, ?
A) 7681 B) 3691 C) 5721 D) 4326
Sol: Here, if we observe the starting and last numbers, they have a big difference between them, so the series is based on difference logic.
3 × 2 − 1 = 5
5 × 4 − 3 = 17
17 × 6 − 5 = 97
97 × 8 − 7 = 769
⇒ 769 × 10 − 9 = 7681
Ans: A
18. 2, 1, 1, 2, 8, ?
A) 4 B) 16 C) 64 D) 18
Sol: Here, the series in the starting decreased and there after it keeps on increasing. So, initially it should be multiplied by a number which is less than one.
2 × 0.5 = 1
1 × 1 = 1
1 × 2 = 2
2 × 4 = 8
8 × 8 = 64
Ans: C
19. 2, 1, 1, 2, 4, ?
A) 4 B) 6 C) 8 D) 7
Sol: This is also same as above series almost, but here the previous logic fails. So, as the numbers are close to each other, we can go with the difference logic
⇒ Next number = 4 + 3 = 7
Ans: D
20. 33, 165, 825, ?, 20625
A) 3605 B) 4125 C) 5625 D) 3160
Sol: Here, the difference between the starting and ending numbers is more, so, we can go with the product logic. 33 × 5 = 165; 165 × 5 = 825
825 × 5 = 4125; 4125 × 5 = 20625
Ans: B
21. 1716, 990, 504, 210, 60, ?
A) 12 B) 8 C) 6 D) 10
Sol: Here, if we observe clearly all the numbers are close to cubes.
123 − 12 = 1716; 103 − 10 = 990
8 3 − 8 = 504; 63 − 6 = 210
4 3 − 4 = 60
2 3 − 2 = 6
Ans: C
