What does the ! mean in math formulas?

by Richard
(USA)

Question
I was taking an online test and the question was what does 4! mean. Do you know what this means?
Answer
It's the factorial sign (!). 4! simply means that we are taking the product of 4×3×2×1. See some examples below:

1! = 1
2! = 2×1 = 2
3! = 3×2×1 = 6
4! = 4×3×2×1 = 24
5! = 5×4×3×2×1 = 120

In general:
n! = n×(n-1)× (n-2)× .... ×3×2×1

That's all.

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Jun 10, 2015
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Jun 03, 2015
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May 10, 2015
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Jan 14, 2015
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Dec 08, 2014
Great
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Oct 10, 2009
helpful
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