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Permutation/Combination....

by Shadow » Tue Jul 10, 2007 10:05 pm
A certain restaurent offers 6 kinds of cheese and 2 kinds of fruit for its dessert platter. If each dessert platter contains an equal number of kinds of cheese and kinds of fruit, how many different dessert platters could the restaurent offer?

A. 8
B. 12
C. 15
D. 21
E. 27
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by givemeanid » Wed Jul 11, 2007 5:41 am
The restaurant can offer a platter with 1Cheese,1Fruit OR 2Cheese,2Fruits

1Cheese,1Fruit = 6C1*2C1
2Cheese,2Fruit = 6C2*2C2

Total number of platters restaurant can offer = 6C1*2C1 + 6C2*2C2 = 6*2 + 15*1 = 27
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by jrbrown2 » Thu Jul 12, 2007 3:46 pm
The restaurant can offer a platter with 1Cheese,1Fruit OR 2Cheese,2Fruits

1Cheese,1Fruit = 6C1*2C1
2Cheese,2Fruit = 6C2*2C2

Total number of platters restaurant can offer = 6C1*2C1 + 6C2*2C2 = 6*2 + 15*1 = 27
Givemeanid,

Can you explain how to compute the 6C1, 6C2. I completely forgot how to compute those. And when is it necessary to use them?
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by givemeanid » Thu Jul 12, 2007 5:45 pm
nCk = n! / (k! * (n-k)!)
nPk = n! / (n-k)!
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