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Mgmat combos question

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Jinglander
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Mgmat combos question [#permalink] New post   24 Sep 2010, 18:15
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A
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E

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Ok here is a problem from mgmat that I don't agree with the answer. Please advise

Amy and Adam are making boxes of truffles for as wedding favors. They have an unlimited supply of 5 different types of truffles. If each box holds 2 truffles of different types how many different boxes can they make.

The book says it's 5!/3!2! but this seems wrong since there is a unlimited supply. Instead I would think u have 5 choices for the first and 4 for the second hense 20

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Re: Mgmat combos question [#permalink] New post   24 Sep 2010, 18:25
Jinglander wrote:
Ok here is a problem from mgmat that I don't agree with the answer. Please advise

Amy and Adam are making boxes of truffles for as wedding favors. They have an unlimited supply of 5 different types of truffles. If each box holds 2 truffles of different types how many different boxes can they make.

The book says it's 5!/3!2! but this seems wrong since there is a unlimited supply. Instead I would think u have 5 choices for the first and 4 for the second hense 20

Posted from my mobile device

There's an unlimited supply, but that is irrelevant since the question specifies that each box must hold two different types of truffles. Therefore it is 5c2.

Picking 20 as an answer assumes order matters but it doesn't because {A,B} is the same box of truffles as {B,A}.
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Re: Mgmat combos question [#permalink] New post   25 Sep 2010, 09:30
Well. Hope below ans help you.
They have an unlimited supply of 5 different types of truffles. So, total truffles available are = 5 types only..
Out of 5, you can fix 2 turffles in a box ===> from 5 u need to select 2 ===> 5c2 = 5!/(5-2)!2!

===> 5!/3!2!


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Re: Mgmat combos question [#permalink] New post   25 Sep 2010, 12:12
Jinglander wrote:
Ok here is a problem from mgmat that I don't agree with the answer. Please advise

Amy and Adam are making boxes of truffles for as wedding favors. They have an unlimited supply of 5 different types of truffles. If each box holds 2 truffles of different types how many different boxes can they make.

The book says it's 5!/3!2! but this seems wrong since there is a unlimited supply. Instead I would think u have 5 choices for the first and 4 for the second hense 20

Posted from my mobile device


It is a test of combination concept since a box with 2 truffles AB or BA are considered to be the same and hence you need to divide the result of (First choice of truffle * second choice) of truffles --> 5*4 by 2.

This leads to the answer given in the book --- 5!/((2!)*(3!)) -- 10.
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Re: Mgmat combos question [#permalink] New post   25 Sep 2010, 13:21
To use MGMAT's anagram method, let Y = included and N = not included. This would give YYNNN. So it would be 5!/(3!2!).
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Re: Mgmat combos question [#permalink] New post   25 Sep 2010, 16:35
The questions asks "how many different boxes can they make". The unlimited supply is irrelevant.

Therefore 5!/(2!*3!) = 10
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Re: Mgmat combos question [#permalink] New post   11 Oct 2010, 04:09
Jinglander wrote:
Amy and Adam are making boxes of truffles for as wedding favors. They have an unlimited supply of 5 different types of truffles.

Bag of 5 choices.

Jinglander wrote:
If each box holds 2 truffles of different types

Combo box arrangement
(_)(_)/2!

Jinglander wrote:
how many different boxes can they make.

First position has 5 choices. Second position has 4 choices.
(5)(4)/2!

Jinglander wrote:
The book says it's 5!/3!2!


5!/3!2! = (5)(4)(3)(2)(1)/(3)(2)(1)(2)(1) = (5)(4)/2!



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Re: Mgmat combos question [#permalink]
11 Oct 2010, 04:09
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