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### Factorials

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Date: 2/3/96 at 22:20:17
From: Anonymous
Subject: 3!

What does 3! mean?  I've looked it up in my math book index about 40
times,but I'm only in fourth grade, so I might not find it there.
```

```
Date: 3/21/96 at 19:48:3
From: Doctor Ken
Subject: Re: 3!

Hello!

3! is a neat thing.  It's said "three factorial," and it means
3 x 2 x 1.

Similarly, 7! (seven factorial) means 7 x 6 x 5 x 4 x 3 x 2 x 1.
And so on.

Here are a couple of other things about factorials: 1! = 1, which pretty
much makes sense.  What's more, 0! = 1, which is really wacky.  But I'm
afraid it's just defined that way.

Thanks for the question!

-Doctor Ken,  The Math Forum

```
Associated Topics:
Elementary Definitions
Middle School Definitions
Middle School Factorials

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