AccipiterQ wrote:
VeritasPrepKarishma wrote:
Understand here that 37 is the number of people, not the number of instances. Hence 6 is not counted 3 times in 37.
Out of 37 people, 18 people cannot do all three. Only 6 can do all three. So 31 can do exactly 2 things.I have discussed this concept in my blog post given below:
http://www.veritasprep.com/blog/2012/09 ... ping-sets/Question 1 on the diagram is this.
How do you know that's true though; to me the question read like every other overlapping data set question. It didn't specify 'exactly' two, and seemed to be worded as other questions which mention people being in at least two sets...
The statement given in the question is this:
"If the number of people who could do at least two of these things, was found to be 37 and the number of people who could do all these things was found to be 6"
Say, I have 37 people in front of me and I say that these are the people who can do at least two of the three things - say these people are P1, P2, ...P37.
I also know that exactly 6 people can do all three things. These 6 are P1, P4, P8, P9, P10, P12
Tell me, how many people can do exactly 2 of the three things? 31 or 19? The answer here is 31.
Note that this situation is different from the usual: 10 people can swim and dance, 20 people can dance and drive and 7 people can swim and drive. In this case, each of the 10, 20 and 7 includes the people who can do all 3 things and hence 10 + 20 + 7 - 6*3 = 19 people can do exactly two things.
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Karishma
Veritas Prep GMAT Instructor
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