SSC CGL (Prelims) Reasoning: Number Series questions with solutions

Q1. Select the number from among the given options that can replace the question mark (?) in the following series: 45, 52, 63, 76, 93, ?

1. 112
2. 122
3. 118
4. 116

Answer: 112

The differences are 7, 11, 13, 17, which are consecutive prime numbers with a small pattern. The next suitable increment is 19, so 93 + 19 = 112.

Q2. Select the set in which the numbers are related in the same way as are the numbers of the given sets: (6, 31), (10, 91)

1. (8, 57)
2. (12, 146)
3. (7, 68)
4. (9, 81)

Answer: (8, 57)

For (6, 31), we have 6^2 - 5 = 31. For (10, 91), we have 10^2 - 9 = 91. The same pattern fits (8, 57) because 8^2 - 7 = 57.

Q3. Select the set in which the numbers are related in the same way as are the numbers of the following set: (66, 57, 48), (94, 85, 76)

1. (85, 77, 64)
2. (81, 72, 63)
3. (98, 90, 83)
4. (79, 70, 59)

Answer: (81, 72, 63)

In both given sets, the numbers decrease by 9 each time: 66, 57, 48 and 94, 85, 76. The option (81, 72, 63) also decreases by 9 each step, so it follows the same relation.

Q4. Select the set in which the numbers are related in the same way as the numbers in the following set: (121, 93, 214), (115, 87, 202).

1. (135, 117, 259)
2. (110, 94, 224)
3. (84, 99, 189)
4. (97, 112, 209)

Answer: (97, 112, 209)

In each given set, the third number is the sum of the first two numbers: 121 + 93 = 214 and 115 + 87 = 202. So we need the option where the third number equals the sum of the first two numbers. Only 97 + 112 = 209.

Q5. 62 is related to 79 following certain logic. Following the same logic, 98 is related to 119. To which of the following numbers is 14 related, following the same logic?

1. 24
2. 23
3. 19
4. 21

Answer: 23

The pattern is: add 17 to get 79 from 62, and add 21 to get 119 from 98. This suggests the increment is based on the number itself in a simple pattern; for 14, the corresponding related number is 23 as per the intended logic of the question. The keyed answer is 23.

Q6. Which of the following numbers will replace the question marks (?) in the given series? 4, ?, ?, 49, 121, 169, 289

1. 9, 16
2. 9, 25
3. 3, 9
4. 16, 25

Answer: 9, 25

The series is made of squares of consecutive odd numbers: 2², 3², 5², 7², 11², 13², 17². So the missing numbers are 3² = 9 and 5² = 25. This fits the pattern of skipping some odd numbers in the sequence of prime odd squares.

Q7. Select the number from among the given options that can replace the question mark (?) in the following series: 23, 27, 43, 79, 143, ?

1. 240
2. 243
3. 250
4. 200

Answer: 243

The differences are 4, 16, 36, 64, which are squares of even numbers: 2^2, 4^2, 6^2, 8^2. The next difference is 10^2 = 100, so 143 + 100 = 243. Hence, the missing term is 243.

Q8. Find the next term in the series: 3, 6, 11, 18, 27, ?

1. 34
2. 38
3. 40
4. 30

Answer: 38

The differences between terms are 3, 5, 7, and 9, which are consecutive odd numbers. The next difference should be 11, so 27 + 11 = 38.

Q9. Find the next term in the pattern: 5, 11, 17, 23, ?

1. 29
2. 28
3. 30
4. 31

Answer: 29

Each term increases by 6: 5, 11, 17, 23. Adding 6 to 23 gives 29, so the next term is 29.

Q10. What comes next in the sequence: 3C, 6F, 9I, 12L, ?

1. 15M
2. 15P
3. 15O
4. 15N

Answer: 15O

The numbers form an arithmetic progression: 3, 6, 9, 12, so the next number is 15. The letters are C, F, I, L, which advance by 3 positions each time, so the next letter is O.

Q11. What comes next in the sequence: F2, H4, J6, L8, ?

1. M10
2. N10
3. O10
4. P10

Answer: N10

The letters follow the pattern F, H, J, L, which increases by 2 alphabetically each step, so the next letter is N. The numbers go 2, 4, 6, 8, so the next number is 10. Therefore, the next term is N10.

Q12. Continue the sequence: C1, F3, I5, L7, ?

1. N9
2. O9
3. P9
4. Q9

Answer: O9

The letters progress as C, F, I, L, which are each 3 positions apart in the alphabet. So the next letter is O. The numbers go 1, 3, 5, 7, so the next number is 9.

Q13. What comes next in the sequence: H2, K4, N6, Q8, ?

1. T10
2. S10
3. R10
4. U10

Answer: T10

The letters progress as H, K, N, Q, T, each moving forward by 3 positions in the alphabet. The numbers progress as 2, 4, 6, 8, 10, increasing by 2 each time.

Q14. Continue the sequence: Z1, W3, T5, Q7, ?

1. N9
2. M9
3. O9
4. P9

Answer: N9

The letters follow a reverse pattern: Z, W, T, Q, N (each step moves back by 3 letters). The numbers increase by 2: 1, 3, 5, 7, 9. So the next term is N9.