What Series Questions Test
- Number series — differences, squares, mixed rules
- Letter series — alphabet gaps and cycles
- Alphanumeric series — combined letter-number terms
- Series completion and wrong-term spotting
Question bank coverage by sub-pattern
How Series Appears in SSC CPO
Series is part of the General Intelligence & Reasoning section (25% of the SSC CPO syllabus).
Series Solved Examples for SSC CPO
12 exam-pattern series questions from the practice bank, each with a full solution.
Find the missing number in the series: 7, 11, 20, 36, 61, ?
- A.97Correct
- B.99
- C.95
- D.101
Solution
Differences: 11-7=4, 20-11=9, 36-20=16, 61-36=25. Second differences: 9-4=5, 16-9=7, 25-16=9. Third differences: 7-5=2, 9-7=2. Constant third difference of 2. Next second difference = 9+2=11. Next first difference = 25+11=36. Next term = 61+36=97.
Find the next term: 2, 3, 5, 7, 11, 13, ?
- A.15
- B.17Correct
- C.19
- D.14
Solution
This is the series of prime numbers. 2, 3, 5, 7, 11, 13 — the next prime number is 17.
What comes next in the following series: aba ababa ababa ?
- A.abaCorrect
- B.bab
- C.aab
- D.baa
Solution
The series follows a repeating pattern of 'aba ababa ababa aba'. Therefore, the next group of letters is 'aba'.
Find the missing number: 4, 9, 25, 49, 121, ?
- A.144
- B.169Correct
- C.196
- D.225
Solution
These are squares of prime numbers: 2^2=4, 3^2=9, 5^2=25, 7^2=49, 11^2=121. The next prime is 13, so 13^2=169.
Find the next term: A2C, E4G, I6K, ?
- A.M8OCorrect
- B.L8N
- C.M8N
- D.N8P
Solution
First letter: A, E, I, M (every 4th letter, i.e., +4). Number: 2, 4, 6, 8 (+2). Third letter: C, G, K, O (every 4th letter, i.e., +4). So the next term is M8O.
Find the next term in the series: ZA, YB, XC, WD, ?
- A.VECorrect
- B.UE
- C.VF
- D.UF
Solution
First letter goes backward: Z, Y, X, W, V. Second letter goes forward: A, B, C, D, E. Next term: VE.
Find the missing term in the series: AZ, BY, CX, DW, ?
- A.EVCorrect
- B.EU
- C.FV
- D.EX
Solution
The first letter advances by 1: A, B, C, D, E. The second letter goes backward by 1: Z, Y, X, W, V. So the next term is EV.
Find the missing number in the series: 1, 4, 27, 256, ?
- A.3125Correct
- B.625
- C.1024
- D.3025
Solution
The pattern is n^n. 1^1=1, 2^2=4, 3^3=27, 4^4=256, 5^5=3125.
Find the missing number in the series: 2, 6, 18, 54, ?
- A.108
- B.162Correct
- C.148
- D.156
Solution
Each term is multiplied by 3 to get the next term. 2 x 3 = 6, 6 x 3 = 18, 18 x 3 = 54, 54 x 3 = 162.
Find the missing term in the series: QPO, NML, KJI, ?
- A.HGFCorrect
- B.FED
- C.GFE
- D.HGE
Solution
Each group consists of three consecutive letters in reverse order. QPO: Q(17),P(16),O(15). NML: N(14),M(13),L(12). KJI: K(11),J(10),I(9). Next: H(8),G(7),F(6) = HGF.
Find the wrong number in the series: 3, 7, 15, 31, 63, __(pick wrong)__ __(pick)____(pick)__125
- A.__(pick)____(pick)__7
- B.15
- C.__(pick)____(pick)__31
- D.125Correct
Solution
Pattern: each term = previous term × 2 + 1. 3×2+1=7, 7×2+1=15, 15×2+1=31, 31×2+1=63, 63×2+1=127 (not 125). The wrong number is 125; it should be 127.
Find the wrong number in the series: 2, 9, 28, 65, 126, 216
- A.9
- B.28
- C.65
- D.216Correct
Solution
The pattern is n^3 + 1. 1^3+1=2, 2^3+1=9, 3^3+1=28, 4^3+1=65, 5^3+1=126, 6^3+1=217. The last term should be 217, not 216. Hence, 216 is the wrong number.
Series — Frequently Asked Questions
How are letter series decoded quickly?
Convert letters to positions (A=1 … Z=26) and treat it as a number series. Gaps of +2/+3, alternating jumps and reversals become obvious as numbers.
What distinguishes SSC series questions from banking ones?
SSC leans on letter and figure series alongside numeric ones, while banking papers focus on numeric series. Practising all three families covers both patterns.
How many Series practice questions does Parikshala have for SSC CPO?
57 exam-pattern Series questions for SSC CPO Reasoning, each with a step-by-step solution. Practice is free — no sign-up needed to start.