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probablity dessert platters

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poonamchiK
 Post subject: probablity dessert platters
 Post Posted: Sun Aug 29, 2010 3:10 am 
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Students


Posts: 104
In a resturant's dessert paltter, there are 6 different kinds of cheese and 2 different kinds of fruits. If each platter consists of equal no. of cheese and fruits, how many different platters can be made?
a. 8
b. 12
c. 15
d. 21
e 27

correct ans : e
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accounts
 Post subject: Re: probablity dessert platters
 Post Posted: Sun Aug 29, 2010 2:03 pm 
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Forum Guests


Posts: 9
We need equal number of cheese and fruits to make a platter. This can be done when

(1 type of cheese and 1 type of fruit) OR (2 type of cheese and 2 type of fruits)

Note: as types of fruits are 2 and types of cheese 6 ... fruits become the deciding factor.

( 6C1 X 2C1) OR ( 6C2 x 2C2 )
(6*2) + (15 x1 )
= 27 => E
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RonPurewal
 Post subject: Re: probablity dessert platters
 Post Posted: Thu Sep 16, 2010 7:02 am 
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ManhattanGMAT Staff


Posts: 6765
accounts wrote:
We need equal number of cheese and fruits to make a platter. This can be done when

(1 type of cheese and 1 type of fruit) OR (2 type of cheese and 2 type of fruits)

Note: as types of fruits are 2 and types of cheese 6 ... fruits become the deciding factor.

( 6C1 X 2C1) OR ( 6C2 x 2C2 )
(6*2) + (15 x1 )
= 27 => E


this works.

as an alternative, note that you should easily be able to LIST the possibilities in the time given, and then COUNT the items in your list. (to facilitate this, it's best to call the cheeses 1, 2, 3, 4, 5, 6 and the fruits 1 and 2.)

try making this list; make sure that you can do so in well under the two-minute guideline.
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