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Combination

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Junior | Next Rank: 30 Posts
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Combination

by gxj007 » Sun Sep 13, 2009 5:57 pm
Can anyone exlpain how to work this problem?


A decorator is to select 2 chairs and 2 tables from a collection of chairs and tables in a warehouse that are all different from each other. If there are 5 chairs in the warehouse and if 150 different combinations are possible, how many tables are in the warehouse?

6
8
10
15
30


Answer:
6
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by praky_rules » Sun Sep 13, 2009 7:35 pm
number of tables = n say
nC2*5C2=150

n*(n-1)/2 x 5*4/2 = 150 so n =6.
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