Factorial

Definition of Factorial

• Factorial denoted as n!, with n > 0, is an expression which is the product of all positive intergers starting with n and counting backward to 1.

For example, 4! = 4 . 3 . 2 . 1 and

                      n! = n . n-1 .  n-2 . . . . 3. 2. 1

More about Factorial

• By definition, factorial of zero is 1.

That is, 0! = 1

Solved Example on Factorial

Find the factorial of 8.

Choices:

A. 40,320

B. 40,230

C. 41,320

D. 41,230

Correct Answer:  A

Solution:

Step 1: Factorial of 8 is 8 × 7 × 6 × 5 × 4 × 3 × 2 × 1  = 40,320.

Related Terms for Factorial

• Integer
• Expression
• Product

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