Factorial (n!)
How to solve the factorial of a number (n!): formula, examples, and their solutions.
Definition
n! means
multiply from n to 1.
So n! = n⋅(n - 1)⋅(n - 2) ... 3⋅2⋅1.
[ ! ] is read as [factorial].
Example 1
5! is
multiplying from 5 to 1.
So 5! = 5⋅4⋅3⋅2⋅1.
5⋅4 = 20
3⋅2 = 6
20⋅6 = 120
So 120 is the answer.
Example 2
7! is
multiplying from 7 to 1.
But, instead of writing 7⋅6⋅5⋅[4⋅3⋅2⋅1] / 4!,
write 7⋅6⋅5⋅[4!] / 4!.
By writing [4!],
you can solve this easier:
you can cancel this [4!] and the denomiantor's 4!.
(dark gray)
Cancel 4! (dark gray)
in both of the numerator and the denominator.
Then (given) = 7⋅6⋅5.
6⋅5 = 30
7⋅30 = 210
So 210 is the answer.
Example 3: 1!
1! is 1.
This is because
1! means
multiply from 1 to 1.
Example 4: 0!
0! is defined as 1.
So 0! = 1.
