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# At a certain laboratory, chemical substances are identifies

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At a certain laboratory, chemical substances are identifies [#permalink]  31 Jan 2008, 22:03
At a certain laboratory, chemical substances are identifies by an unordered combination of 3 colors. If no chemical may be assigned the same 3 colors, what is the maximum number of substances that can be identified using 7 colors?

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Director
Joined: 01 May 2007
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Re: combs color coding [#permalink]  01 Feb 2008, 10:29
Concur using anagram:

7*6*5*4*3*2*1 (Order does not matter)
Y Y Y N N N N

7!/(3!4!)
CEO
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Re: combs color coding [#permalink]  01 Feb 2008, 13:42
marcodonzelli wrote:
At a certain laboratory, chemical substances are identifies by an unordered combination of 3 colors. If no chemical may be assigned the same 3 colors, what is the maximum number of substances that can be identified using 7 colors?

21
35
105
135
210

7!/3!4! b/c lets say we have color ABC BCA is the same thing (order does not matter)

So C 35.
Re: combs color coding   [#permalink] 01 Feb 2008, 13:42
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