Factorial-Vowel Series

Factorial-Vowel series alternate between factorial numbers (1! = 1, 2! = 2, 3! = 6, 4! = 24, 5! = 120...) and vowels (A, E, I, O, U). These advanced problems test your knowledge of factorial values and vowel patterns.

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Introduction to Factorial-Vowel Series

Factorial-Vowel series alternate between factorial numbers (1! = 1, 2! = 2, 3! = 6, 4! = 24, 5! = 120...) and vowels (A, E, I, O, U). These advanced problems test your knowledge of factorial values and vowel patterns.

Prerequisites

Factorial numbers (1! = 1, 2! = 2, 3! = 6, 4! = 24, 5! = 120, 6! = 720...) Vowel order (A, E, I, O, U, A...) Modulo for large factorials Alternating pattern recognition
Why This Matters: Factorial-Vowel series problems appear in 1-2 questions in Banking PO and SSC CGL exams. They test factorial knowledge and vowel pattern recognition.

How to Solve Factorial-Vowel Series Problems

1

Step 1: Identify whether the series starts with a factorial number or a vowel

2

Step 2: For factorial numbers, calculate the next factorial in the sequence

3

Step 3: For vowels, follow the cyclic vowel order (A→E→I→O→U→A)

4

Step 4: Determine which type (factorial or vowel) the next term will be

5

Step 5: Calculate the next factorial or identify the next vowel

6

Step 6: For large factorials, use modulo for wrap-around if converting to letters

7

Step 7: Present the next term

Pro Strategy: Factorials progress in order: 1!, 2!, 3!, 4!, 5!... Vowels follow the cyclic order: A, E, I, O, U, A... The pattern alternates between the two sequences.

Example Problem

Example: Find the next term: 1, A, 2, E, 6, I, 24, O, ___ Solution: Step 1: Pattern: factorial, vowel, factorial, vowel... Step 2: Factorials: 1!=1, 2!=2, 3!=6, 4!=24 Step 3: Vowels: A, E, I, O (cyclic order: A→E→I→O→U→A) Step 4: Next is 9th term (odd) → factorial Step 5: Next factorial = 5! = 120 Answer: 120

Pro Tips & Tricks

  • Factorials: 1! = 1, 2! = 2, 3! = 6, 4! = 24, 5! = 120, 6! = 720, 7! = 5040, 8! = 40320
  • Vowel cycle: A → E → I → O → U → A (positions 1,5,9,15,21)
  • For factorial numbers > 26, they can be converted to letters using modulo 26 for position-based series
  • The pattern may start with either factorial or vowel
  • Both sequences progress in natural order

Shortcut Methods to Solve Faster

Next factorial = (n+1)! where n is the current factorial index
Next vowel = next vowel in cycle: A→E→I→O→U→A
Factorial sequence: 1,2,6,24,120,720,5040,40320,362880...
Vowel sequence: A,E,I,O,U,A,E,I,O,U...

Common Mistakes to Avoid

Miscalculating factorials (e.g., 3! = 6, not 9; 4! = 24, not 12)
Forgetting that 0! = 1 (some series may start with 0!)
Not knowing factorials beyond 5!
Confusing vowel order (e.g., placing O before I)
Forgetting that vowel cycle wraps from U back to A

Exam Importance

Factorial-Vowel 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
CAT
1-2 questions
INSURANCE
1-2 questions

Ready to Master Factorial-Vowel 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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