GDS General Intelligence & Reasoning: Series Completion — Concept Guide + MCQs

Series Completion — Letters, Numbers & Mixed

Series completion tests pattern recognition in sequences of letters, numbers, or both. You must identify the rule and supply the next or missing term.

Types of Series

  • Letter Series: A, D, G, J, ? (skipping 2 letters each time)
  • Number Series: 2, 6, 12, 20, ? (differences: 4,6,8,10 → 30)
  • Alphanumeric Series: A2, C4, E6, G8, ? (I10)
  • Mixed Pair Series: AZ, BY, CX, ? (DW — first letter ascending, second descending)
  • Month/Day Series: Jan, Mar, May, ? (Jul — alternate months)

Shortcut Tricks for Letter Series

EJOTY trick: E=5, J=10, O=15, T=20, Y=25 — helps you quickly find letter positions.
Step 1: Convert letters to numbers (A=1 to Z=26).
Step 2: Find the difference pattern in numbers.
Step 3: Apply the same pattern to get the next number, convert back to letter.
For mixed series: Track the number component and letter component separately.

Alphabet Position Quick Reference

A=1B=2C=3D=4E=5F=6G=7
H=8I=9J=10K=11L=12M=13N=14
O=15P=16Q=17R=18S=19T=20U=21
V=22W=23X=24Y=25Z=26

Practice MCQs

Q1. AZ, BY, CX, DW, ?

  • A) EV
  • B) EU
  • C) FV
  • D) EW

Answer: A — Pairs: A+Z, B+Y, C+X, D+W → E+V = EV.

Q2. Z, X, V, T, R, ?

  • A) P
  • B) O
  • C) Q
  • D) N

Answer: A — Alternate letters descending: Z,X,V,T,R → P.

Q3. A, D, G, J, M, ?

  • A) P
  • B) O
  • C) Q
  • D) N

Answer: A — +3 each: A(1),D(4),G(7),J(10),M(13) → P(16).

Q4. AB, CD, EF, GH, ?

  • A) IJ
  • B) IK
  • C) HI
  • D) JK

Answer: A — Consecutive letter pairs: AB,CD,EF,GH → IJ.

Q5. 1A, 2B, 3C, 4D, ?

  • A) 5E
  • B) 5F
  • C) 6E
  • D) 4E

Answer: A — Number increments +1, letter increments +1: 5E.

Q6. ACE, BDF, CEG, DFH, ?

  • A) EGI
  • B) EHI
  • C) EGJ
  • D) FGI

Answer: A — Each letter in triplet +1: C→D→E, E→F→G, G→H→I → EGI.

Q7. ZA, YB, XC, WD, ?

  • A) VE
  • B) VF
  • C) UE
  • D) WE

Answer: A — First letter descends (Z,Y,X,W,V); second ascends (A,B,C,D,E) → VE.

Q8. B, D, G, K, P, ?

  • A) V
  • B) U
  • C) W
  • D) X

Answer: A — Differences: 2,3,4,5,6 → P+6=V.

Q9. M, N, P, S, W, ?

  • A) B
  • B) A
  • C) C
  • D) D

Answer: A — Differences: +1,+2,+3,+4,+5 → W+5=B (wrapping: W=23, 23+5=28=B(2) in 26-letter cycle).

Q10. Y, W, T, P, K, ?

  • A) E
  • B) F
  • C) G
  • D) D

Answer: A — Differences: –2,–3,–4,–5,–6 → K(11)–6=E(5).