Factorial - Casio fx-82MS Manual Book

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Mastering the Calculator using the Casio fx-82MS
8.

Factorial

Look at your calculator and find the key with the symbol x! on it. You will come across this
symbol when doing the Binomial Distribution. This is called the factorial key.
Use the shift key
to activate x!
Use it to find the 3! and 5!. Press
3! means 3 × 2 × 1
3! = 6
How many ways would you guess that we could arrange ten people?
That is, how large would you estimate 10! to be? Use your calculator to find 10!
You should get 3 628 800.
10! = 10 × 9 × 8 × ... × 3 × 2 × 1
(Thank goodness this can be done on the calculator.)
Factorial rule
The number of ways of arranging n items in order is known as 'factorial n' which is
symbolised as n! where:
n! = n × (n – 1) × (n – 2) × ... × 3 × 2 × 1
x
!
and 5! = 5 × 4 × 3 × 2 × 1
5! = 120