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GMAT Prep PS - 2 Questions - Sets+Probability

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by AleksandrM » Sun Aug 17, 2008 5:56 pm
For the second one, draw a Venn diagram with three circles. Name these circles A, B, and C. As the problems states, the intersection of A and C = 17, intersection of A and B = 16, intersection of B and C = 18. What you are looking for is that little area at the center where A, B and C meet (marked "x" in my image). All you need to know in order to find that value is to know how much of AB is in C, AC is in B, CB is in A.

Statement one tells you that of the 16 elements in AB, 9 are in C. Sufficient.

Statement two provides you with the totals. You cannot figure out the intersection of ABC from this. Insufficient.

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Re: GMAT Prep PS - 2 Questions - Sets+Probability

by GoMBA » Sun Aug 17, 2008 11:26 pm
For the probability question here's my explanation:

For the first ride, total number of options are 3c1 = 3 & number of favorable options is 3c1 = 3 (because he can sit in any car, no preference)
i.e. 3/3 =1

For the second ride, total number of options again are 3c1 = 3 but the number of favorable options is 2c1 = 2 (because he wants to sit in any of the remaining two cars)
i.e. 2/3

For the third ride, total number of options again are 3c1 = 3 & number of favorable options = 1c1 = 1 (because he wants to sit in the only one car left that he has not sat till now)
i.e. 1/3

Hence net probability = 1*2/3*1/3 = 2/9


rishi235 wrote:Hi...
Someone please explain the problems attached herewith.

Thanks...
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by rishi235 » Mon Aug 18, 2008 7:14 am
Thank u both 4 ur explanations :)
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