Dear Maths Help,
I hope you do not mind me troubling you with a question. I am seventy-nine years old, and try to keep my mind active by doing mathematics problems and "surfing" the internet.
My question is: what does the exclamation mark mean when it is written after a number? I came across it in the answer section to a book of mathematical puzzles.
The exclamation mark symbol is pronounced "factorial" when used in mathematics.
It is shorthand for what you get when you multiply the given number (which must be a positive whole number) by
all the smaller whole numbers down to 1.
So you can see that factorials get quite big very quickly.
Two "special cases" are:
Factorials have several applications. The most common one is:
|N different items can be placed in a row in N! different ways|