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Alternate Series

Alternate Series problems present sequences where letters and numbers appear in alternating positions (e.g., A, 2, C, 4, E, 6). These problems test your ability to handle two interleaved sequences.

10Worksheets
200+Practice Questions
IntermediateDifficulty
2-3 hoursHours to Master

What You'll Learn

Introduction & Overview Why This Matters How to Solve Pro Tips & Tricks
Shortcut Methods Common Mistakes Practice Worksheets Exam Importance

Introduction to Alternate Series

Alternate Series problems present sequences where letters and numbers appear in alternating positions (e.g., A, 2, C, 4, E, 6). These problems test your ability to handle two interleaved sequences.

Prerequisites

Alphabet positions Number patterns Interleaved sequence analysis Pattern separation
Why This Matters: Alternate Series problems appear in 1-2 questions in competitive exams. They test the ability to separate and analyze interleaved patterns.

How to Solve Alternate Series Problems

1

Step 1: Separate odd-position terms and even-position terms into two sequences

2

Step 2: Analyze the pattern of odd-position terms (usually letters)

3

Step 3: Analyze the pattern of even-position terms (usually numbers)

4

Step 4: Determine the next term's position (odd or even)

5

Step 5: Apply the appropriate pattern to find the next term

6

Step 6: Verify both sub-sequences follow consistent patterns

Pro Strategy: Always separate the sequence into two interleaved sequences based on position parity (odd/even). Analyze each independently.

Example Problem

Example: Find the next term: A, 2, C, 4, E, 6, ___ Solution: Step 1: Odd positions (1st,3rd,5th): A, C, E → letters Step 2: Even positions (2nd,4th,6th): 2, 4, 6 → numbers Step 3: Letter pattern: A(1), C(3), E(5) → +2 each time Step 4: Number pattern: 2, 4, 6 → +2 each time Step 5: Next is 7th term (odd position) → next letter = G(7) Step 6: Next term = G Answer: G

Pro Tips & Tricks

  • Write the sequence with position numbers (1st, 2nd, 3rd, etc.)
  • Odd positions often contain one type (letters), even positions contain the other (numbers)
  • The step size may be different for each sub-sequence
  • Sometimes the alternating pattern is letters and letters (two different letter sequences)
  • The pattern may alternate between forward and backward movement
  • Check if the sub-sequences themselves follow arithmetic or geometric progression

Shortcut Methods to Solve Faster

For alternating letters and numbers, the next term type alternates
If odd positions are letters, all odd positions are letters
The pattern in each sub-sequence is usually a simple arithmetic progression

Common Mistakes to Avoid

Trying to find a single pattern for the entire sequence
Misidentifying which terms belong to which sub-sequence
Forgetting to check the parity of the next term's position
Assuming both sub-sequences have the same step size

Exam Importance

Alternate Series is an important topic for various competitive exams. Here's how frequently it appears:

SSC CGL
1-2 questions
BANKING PO
1-2 questions
RAILWAYS RRB
1-2 questions
INSURANCE
1-2 questions

Ready to Master Alternate Series?

Start with Worksheet 1 and work your way up to expert level! Each worksheet includes:

20 practice questions
Detailed solutions
Step-by-step explanations
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