Dr. Cary Oberije, a postdoctoral researcher in The Netherlands, has found that mathematical models can be used to accurately predict patients' responses to treatment. Prediction models were used to analyze lung cancer patients' likelihood of survival and...

# When Will I Use Math?

## WeUseMath.org

# 0! = 1

0! = 1 (zero factorial equals one)

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5! = 5x4x3x2x1 = 120

4! = 4x3x2x1 = 24

3! = 3x2x1 = 6

2! = 2x1 = 2

1! = 1

0! = 1

If n! is the number of ways to put n objects in order, then 0! is the number of ways to put 0 objects in order. The only way to put 0 objects in order is to "Not have any objects." This is 1 way. Therefore 0! = 1.

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It does sound strange to say that 0! equals 1!

( this is not one factorial, just stressing the phrase :-P )

BUT, do you know why 0! = 1 ?

We say that 0! = 1 just for formulas like the binomial coefficient to work,

imagine the “n choose k” scenario, we have:

n!/k!(n-k)!

and we know when n = k this should equals 1, right ? so...

n!/n!(n-n)!

n!/n!0!

If we had that 0! doesn't equal 1, we wouldn't be able to use this formula,

so we all agree that 0! equals 1, and we are happy about that. ;)