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GMAT prep

by rajt » Fri May 18, 2007 2:46 pm
Tu furnish a room in a model home, an interior designer 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?
1. 6
2. 8
3. 10
4. 30
5. 12
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by bww » Fri May 18, 2007 3:15 pm
30 tables?

5Cn=150
5*n=150
n=30
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Re: GMAT prep

by jayhawk2001 » Fri May 18, 2007 3:46 pm
rajt wrote:Tu furnish a room in a model home, an interior designer 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?
1. 6
2. 8
3. 10
4. 30
5. 12
Let number of tables be n

5C2 * nC2 = 150
10 * nC2 = 150

nC2 = 15

n*(n-1) / 2 = 15
n = 6

Is it A?
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by atarafder » Fri May 18, 2007 3:57 pm
I am getting 6 too.
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by rajt » Fri May 18, 2007 4:05 pm
6 is teh right answer. Thanks Jay!
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by Cybermusings » Tue May 22, 2007 5:12 am
5C2 * xC2 = 150
10 * xC2 = 150
xC2 = 15
x*(x-1)*(x-2)! / 2! * (x-2)! = 15
x*x-1 = 15*2!
x*x-1 = 30
Thus x = 6
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by tejpreet » Tue Jun 05, 2007 9:27 pm
The Answer is 6

No. of Chairs= 5C2 = 10
No. of Tables = xC2 =

Total = 10 *xC2 =150
====> 10 *15 =150
====> xC2 = 15
Put x = 6
which is 6C2 = 15

Hence 6 is the Correct Answer
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