Factorial Notation
The expression 6 × 5 × 4 × 3 × 2 × 1 = can be written as 6!, which is read as “six factorial.”
In general, n! is the product of all the counting numbers beginning with n and counting backwards to 1. We define 0! to be 1.
The following diagram describes the factorial notation and gives some examples using factorials. Scroll down the page for more examples and solutions using factorials.
Example:
Find the value of each expression:
a) 3!
b) 0!
c) 5!
d) 1!
e) 3! + 2!
f) 
Solution:
a) 3! = 3 × 2 × 1 = 6
b) 0! = 1
c) 5! = 5 × 4 × 3 × 2 × 1 = 120
d) 1! = 1
e) 3! + 2! = (3 × 2 × 1) + (2 × 1) = 8
f) 
Factorials Explained!
Some basic information on factorials and shows how to evaluate some factorial examples.
Check out our most popular games!
Fraction Concoction Game:
Master fractions in the lab: mix, add, and subtract beakers to create the perfect concoction!
Fact Family Game:
Complete fact families and master the link between addition & subtraction and multiplication & division.
Number Bond Garden:
Clear the board by matching number pairs that sum to ten in this garden-themed mental math puzzle.
Online Addition Subtraction Game:
Practice your addition and subtraction skills to help the penguin find its mummy.
We welcome your feedback, comments and questions about this site or page. Please submit your feedback or enquiries via our Feedback page.