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Lesson: Applied Arithmetic - 22

Factorials

[Page 22 of 36]
Factorials are very simple things. They're just products, indicated by an exclamation mark. For instance, "four factorial" is written as "4!" and means 1×2×3×4 = 24. In general, n! ("enn factorial") means the product of all the whole numbers from 1 to n; that is, n! = 1×2×3×...×n.

You may see the following on a standardized test:

7!

You should not read this to mean: emphatically seven! That exclamation point, as a mathematical symbol, represents the factorial function, and here's what it means:

In other words:

If you see a question involving factorials on a standardized test, you generally won't have to calculate the value of the factorial. Instead, factorial questions tend to test your ability to factor or reduce, so you should take note of the following:

, and so on.

Let's take a look at an in-format question.

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