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Dinda Erliananda Teaching Materials – SMA Class XII – Enumeration Rules

B PERMUTATION

1. Factorial Notation

If there are 3 elements that do not want to be placed in 3 places with a non-circular
position, then the number of different arrangements is 3 x 2 x 1 = 6 ways.

In math the multiplication of 3 x 2 x 1 is denoted by 3! read 3 factorial. Likewise:

(i) 4! = 4 3 2 1
(ii) 5! = 5 4 3 2 1

(iii) 10! = 10 9 8 ... 3 2 1

So, for n positive integers, then:

In this case defined:
and

Example 3:
Calculate:

a. b.

Answer:

a. b.

LET'S WATCH TOGETHER!

Let’s watch this example of permutation before we continue to our next topic:

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