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# At a certain laboratory, chemical substances are identifies

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VP
Joined: 22 Nov 2007
Posts: 1079

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At a certain laboratory, chemical substances are identifies [#permalink]

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31 Jan 2008, 23:03
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

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

Kudos [?]: 660 [0], given: 0

Director
Joined: 01 May 2007
Posts: 794

Kudos [?]: 370 [0], given: 0

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01 Feb 2008, 11:29
Concur using anagram:

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

7!/(3!4!)

Kudos [?]: 370 [0], given: 0

CEO
Joined: 29 Mar 2007
Posts: 2554

Kudos [?]: 500 [0], given: 0

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01 Feb 2008, 14:42
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.

Kudos [?]: 500 [0], given: 0

Re: combs color coding   [#permalink] 01 Feb 2008, 14:42
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