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#1 2008-10-31 06:07:39
- Danbee
- Member
- Registered: 2008-08-28
- Posts: 21
Permutations and combinations
How many four-digit even numbers can be formed if no digit is repeated?
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#2 2008-10-31 06:11:52
- mathsyperson
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- Registered: 2005-06-22
- Posts: 4,900
Re: Permutations and combinations
5*9*8*7 = 2520
Why did the vector cross the road?
It wanted to be normal.
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#3 2008-10-31 06:17:03
- Danbee
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- Registered: 2008-08-28
- Posts: 21
Re: Permutations and combinations
That is not the answer
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#4 2008-10-31 06:35:07
- TheDude
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- Registered: 2007-10-23
- Posts: 361
Re: Permutations and combinations
I think leading 0's is the issue here. How about 9*8*7 = 504 4-digit numbers ending in 0 and 4*8*8*7 = 1792 4-digit even numbers that don't end or begin with 0, for a total of 2296?
Wrap it in bacon
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#5 2008-10-31 10:04:45
- Ricky
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- Registered: 2005-12-04
- Posts: 3,791
Re: Permutations and combinations
Just to expand on what Dude was saying if it wasn't clear, 0123 is not a 4-digit number.
"In the real world, this would be a problem. But in mathematics, we can just define a place where this problem doesn't exist. So we'll go ahead and do that now..."
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#6 2008-10-31 13:33:10
- Danbee
- Member
- Registered: 2008-08-28
- Posts: 21
Re: Permutations and combinations
Thanks for the solution . That is the right answer!
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