## By the Numbers

By the Numbers

In the world of mathematics, a factorial is the product of a whole number and all of the whole numbers below it; for example, four factorial is equal to 24 (4 x 3 x 2 x 1). The symbol to indicate a factorial is ! (an exclamation mark), so four factorial is represented by 4!.

Factorials are used to calculate the probability of something happening or for determining the number of ways things can be arranged. For example, if you have 4 pictures to hang side by side on the wall there are 4! (24) possible arrangements.

That’s it for the math lesson.

Several years ago I was teaching a remedial math course for grade 11 students. The day came for me introduce factorials. At the beginning of class I wrote the following on the board:

5!

OK class, we are about to start a new unit. Before we do that can anyone tell me what this represents on the board?”

The students stared at the symbols. Finally, one of the boys spoke.

Oh, I know.” He took a deep breath and yelled, “FIIIIVE!”, with much gusto.

I wasn’t expecting that reaction at all. It took me a moment to appreciate the humour of the moment.

No doubt, this student responded in a way that many have done before him. I was just happy that it happened in my class.

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