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 RRB NTPC
Series is part of the General Intelligence & Reasoning section (30% of the RRB NTPC syllabus).
Series Solved Examples for RRB NTPC
12 exam-pattern series questions from the practice bank, each with a full solution.
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.
What comes next in the following series: aabca abcabc abcabca ?
- A.bcabcaCorrect
- B.abcabc
- C.aabca
- D.abcab
Solution
The series follows a repeating pattern of 'aabca abcabc abcabca bcabca'. Therefore, the next group of letters is 'bcabca'.
What comes next in the sequence: 0, 7, 26, 63, 124, ?
- A.215Correct
- B.216
- C.255
- D.343
Solution
The series represents the cubes of consecutive natural numbers minus 1: 1^3 - 1 = 0, 2^3 - 1 = 7, 3^3 - 1 = 26, 4^3 - 1 = 63, 5^3 - 1 = 124, 6^3 - 1 = 215.
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.
Find the missing number in the series: 3, 8, 15, 24, 35, ?
- A.46
- B.48Correct
- C.50
- D.42
Solution
Differences between consecutive terms: 8-3=5, 15-8=7, 24-15=9, 35-24=11. The differences increase by 2. Next difference = 13. So 35 + 13 = 48.
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 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 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 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 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.
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 RRB NTPC?
57 exam-pattern Series questions for RRB NTPC Reasoning, each with a step-by-step solution. Practice is free — no sign-up needed to start.