There is a special symbol used in mathematics. It is this exclamation mark "!". And is called the "Factorial" symbol.
It must be attached to a number before meaning forms. Example: 4! and 9!
What does it mean?
Example 1: 4! = 4 x 3 x 2 x 1
Example 2: 9! = 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1
From the above 2 examples, you can see the pattern of the multiplication.
It makes use of the number besides the "!" mark and multiplying all the numbers counted down from it till 1 is reached.
In general: n! = n x ( n - 1 ) x ( n - 2 ) x ( n - 3 ) x ( n - 4 ) x ....... x 1
Real life application:
How many arrangements can we have from a set of 7 different dining plates ?
Answer = 7 x 6 x 5 x 4 x 3 x 2 x 1 ==> Tedious in writing!
Simply with the "!" symbol, we can write, in short-form, the answer as 7!.
Short and easy, instead of writing the chain of numbers.
The invention of Factorial later find its application in calculating permutation of numbers and in exponential definitions.
Isn't mathematics interesting, with its many exciting symbols and their usages? Or is it some lazy man's idea?