Number & Alphabet Series | Delhi Police Exam

1. What are Series?

Series are sequences of numbers or letters that follow a specific pattern or rule. Identifying this pattern helps find missing terms or continue the sequence.

Follows Specific Pattern

Number & Alphabet Sequences

Tests Pattern Recognition

Finds Missing Terms

Simple Definition: Series are ordered sequences where each term follows a logical pattern from the previous ones.

Types of Series

Common Series Patterns

Type	Description	Example
Arithmetic Series	Constant difference between terms	2, 5, 8, 11, 14 (+3)
Geometric Series	Constant ratio between terms	2, 6, 18, 54 (×3)
Alphabet Series	Letter sequences with patterns	A, C, E, G, I (+2 letters)
Mixed Series	Combination of number patterns	1, 4, 9, 16, 25 (Squares)
Alternating Series	Two different patterns alternate	2, 4, 3, 6, 5, 10
Prime Number Series	Sequence of prime numbers	2, 3, 5, 7, 11, 13

2. Number Series Patterns

Common Number Patterns

Arithmetic Progression

Constant addition/subtraction

Example: 5, 8, 11, 14, 17 (+3)

Geometric Progression

Constant multiplication/division

Example: 3, 6, 12, 24, 48 (×2)

Square Series

Squares of numbers

Example: 1, 4, 9, 16, 25 (1²,2²,3²...)

Cube Series

Cubes of numbers

Example: 1, 8, 27, 64, 125 (1³,2³,3³...)

Special Number Patterns

Pattern Type	Rule	Example
Fibonacci Series	Sum of two previous terms	1, 1, 2, 3, 5, 8, 13
Prime Numbers	Numbers divisible by 1 and itself	2, 3, 5, 7, 11, 13
Alternating Pattern	Two different operations alternate	2, 6, 4, 12, 10, 30
Multiplication Pattern	Multiply by increasing numbers	2, 4, 12, 48, 240 (×2,×3,×4,×5)

3. Alphabet Series Patterns

Common Alphabet Patterns

Pattern Type	Description	Example
Constant Gap	Fixed number of letters skipped	A, C, E, G, I (+2 letters)
Increasing Gap	Gap increases progressively	A, B, D, G, K (+0,+1,+2,+3)
Reverse Order	Alphabet in reverse sequence	Z, Y, X, W, V
Vowel Series	Only vowels in sequence	A, E, I, O, U
Consonant Series	Only consonants in sequence	B, C, D, F, G, H
Mixed Pattern	Combination of different patterns	A, Z, B, Y, C, X

4. How to Solve Series Questions?

Follow these step-by-step methods to solve series questions:

1

Check Differences

Find difference between consecutive terms

2

Check Ratios

Look for multiplication/division patterns

3

Identify Pattern Type

Arithmetic, geometric, square, cube, etc.

4

Verify & Find Missing

Apply pattern to find missing term

5. Solved Examples

Example 1: Number Series

Find the missing number: 2, 6, 18, 54, ?

Step 1: Check differences: 6-2=4, 18-6=12, 54-18=36

Step 2: Check ratios: 6÷2=3, 18÷6=3, 54÷18=3

Step 3: Pattern identified: Geometric series (×3)

Step 4: Apply: 54 × 3 = 162

Answer: 162

Example 2: Alphabet Series

Find the missing letter: A, D, G, J, ?

Step 1: Check positions: A=1, D=4, G=7, J=10

Step 2: Pattern: +3 letters each time

Step 3: Apply: J(10) + 3 = M(13)

Answer: M

Example 3: Mixed Series

Find the missing number: 1, 4, 9, 16, ?

Step 1: Check values: 1=1², 4=2², 9=3², 16=4²

Step 2: Pattern: Square of consecutive numbers

Step 3: Apply: 5² = 25

Answer: 25

6. Quick Recap

Series Type	Key Pattern	Example
Arithmetic	Constant difference	5, 8, 11, 14 (+3)
Geometric	Constant ratio	3, 6, 12, 24 (×2)
Square Series	Squares of numbers	1, 4, 9, 16, 25
Alphabet Series	Letter patterns	A, C, E, G (+2)
Fibonacci	Sum of previous two	1, 1, 2, 3, 5, 8

7. Delhi Police Exam Tips

✓

Check differences first - most common pattern

✓

Memorize squares up to 25 and cubes up to 10

✓

Practice alphabet positions - A=1 to Z=26

✓

Look for alternate patterns if simple ones don't work

✓

Time management - skip if taking too long

Series (Number & Alphabet)