Factorial: Types & Uses : What is Factorial ? Types of Factorial & Tricks.

Factorial: Types & Uses

1.     What is Factorial ?

Factorial of a number n is the product of all natural numbers from 1 to n..

n! = n × (n-1) × (n-2) ×...× 1

Ex: 5! = 5 × 4 × 3 × 2 × 1 = 120

Q. In how many different ways can the letters of the word "FACEBOOK" be arranged ?

A) 12160  B) 26342  C) 20160  D) 10080

Solution

The word FACEBOOK has 8 letters: F, A, C, E, B, O, O, K

• Total letters = 8
• The letter O is repeated 2 times.

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