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

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10 Sep 2008, 18:04
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

I know why now, but thought I'd share:

0! = (1-1)! = 1!/1 = 1/1 = 1
SVP
Joined: 29 Aug 2007
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Re: Why is zero factorial equal to one? [#permalink]

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10 Sep 2008, 19:35
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: 129
Followers: 2

Kudos [?]: 19 [0], given: 0

Re: Why is zero factorial equal to one? [#permalink]

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10 Sep 2008, 19:39
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.
Re: Why is zero factorial equal to one?   [#permalink] 10 Sep 2008, 19:39
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