Letter Series

Master the art of solving letter series problems with our comprehensive guide. Learn various patterns, number indexes, and solving techniques.

Table of Contents

Introduction to Letter Series

Letter series problems test your ability to identify patterns and relationships in sequences of letters. Understanding the position of letters in the alphabet is crucial for solving these problems.

Why is it important?

  • Frequently asked in competitive exams (CAT, GMAT, Bank PO, SSC, UPSC)
  • Improves pattern recognition skills
  • Enhances logical thinking abilities

Alphabet Index

Forward Index (A to Z)

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

Reverse Index (Z to A)

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

Common Patterns

1. Simple Forward Series

Letters increase by a fixed number of positions

A, C, E, G, I, ?

Pattern: +2 positions

A(1) → C(3) → E(5) → G(7) → I(9) → K(11)

Answer: K

2. Simple Reverse Series

Letters decrease by a fixed number of positions

Z, X, V, T, R, ?

Pattern: -2 positions

Z(26) → X(24) → V(22) → T(20) → R(18) → P(16)

Answer: P

3. Alternating Series

Two different patterns alternate

A, Z, C, Y, E, X, ?

Pattern 1: +2 positions (A, C, E, ...)

Pattern 2: -1 position (Z, Y, X, ...)

Answer: G

4. Position-Based Series

Letters based on their position numbers

A, B, D, G, K, ?

Pattern: Add position number

A(1) → B(2) → D(4) → G(7) → K(11) → P(16)

Answer: P

5. Mixed Series

Combination of different patterns

A, Z, B, Y, C, X, ?

Pattern 1: Forward series (A, B, C, ...)

Pattern 2: Reverse series (Z, Y, X, ...)

Answer: D

Practice Questions

Question 1

Easy

Complete the series: B, E, H, K, N, ?

Solution:

Pattern: +3 positions

B(2) → E(5) → H(8) → K(11) → N(14) → Q(17)

Answer: Q

Question 2

Medium

Complete the series: Z, X, U, Q, L, ?

Solution:

Pattern: Subtract position number

Z(26) → X(24) → U(21) → Q(17) → L(12) → F(6)

Answer: F

Pro Tips

1. Know Your Alphabet

Memorize the position of each letter in the alphabet.

2. Look for Patterns

Identify if the series is forward, reverse, or alternating.

3. Check for Multiple Patterns

Some series may have more than one pattern.

4. Verify Your Answer

Always check if your answer fits the pattern.