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# I know why now, but thought I'd share: 0! = (1-1)! = 1!/1 =

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Manager
Joined: 30 Jul 2007
Posts: 130
I know why now, but thought I'd share: 0! = (1-1)! = 1!/1 = [#permalink]

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10 Sep 2008, 19:04
I know why now, but thought I'd share:

0! = (1-1)! = 1!/1 = 1/1 = 1

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SVP
Joined: 29 Aug 2007
Posts: 2452
Re: Why is zero factorial equal to one? [#permalink]

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10 Sep 2008, 20:35
sarzan wrote:
I know why now, but thought I'd share:

0! = (1-1)! = 1!/1 = 1/1 = 1

i think its more logical than mathmatical.

suppose there are 5 people. how many group(s) of 5 can be formed from 5 people.

the solution = 5c5 = 5!/[5!(5-5)!] = 5!/(5!0!)

lets use the logic: how many groups of 5 people can be formed from 5 people? 1 group. if we use 0! as 0, then the formula gives infinite groups, which is not correct. so here 0! has to be 1, then only the formula works for all scenarios. therefore, 0! = 1.

we can raise similar question: why $$x^0 = 1$$?

we can apply same logic.
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Manager
Joined: 30 Jul 2007
Posts: 130
Re: Why is zero factorial equal to one? [#permalink]

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10 Sep 2008, 20:39
GMAT TIGER wrote:
sarzan wrote:
I know why now, but thought I'd share:

0! = (1-1)! = 1!/1 = 1/1 = 1

i think its more logical than mathmatical.

suppose there are 5 people. how many group(s) of 5 can be formed from 5 people.

the solution = 5c5 = 5!/[5!(5-5)!] = 5!/(5!0!)

lets use the logic: how many groups of 5 people can be formed from 5 people? 1 group. if we use 0! as 0, then the formula gives infinite groups, which is not correct. so here 0! has to be 1, then only the formula works for all scenarios. therefore, 0! = 1.

we can raise similar question: why $$x^0 = 1$$?

we can apply same logic.

great grasp tiger. thanks for the explanation.

--== Message from GMAT Club Team ==--

This is not a quality discussion. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.
Re: Why is zero factorial equal to one?   [#permalink] 10 Sep 2008, 20:39
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# I know why now, but thought I'd share: 0! = (1-1)! = 1!/1 =

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