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OG PS #239

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Guest
 Post subject: OG PS #239
 Post Posted: Thu Sep 20, 2007 12:31 am 
Hello,

I have a question about the following question from OG:

Of the 200 students at College T majoring in one or more of the sciences, 130 are majoring in chemistry and 150 are majoring in biology. If at least 30 of the students are not majoring in either chemistry or biology, then the number of students majoring in both chemistry and biology could be any number from:

A) 20 to 50
B) 40 to 70
C) 50 to 130
D) 110 to 130
E) 110 to 150

If you use the double set matrix method, shouldn't there only be one answer? i.e. 110? How would you get other answers?

Thank you for your help!
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GMATAttack
 Post subject: Response...
 Post Posted: Thu Sep 20, 2007 4:25 pm 
Tricky sets problem - the words "at least 30 of the students are not majoring in either chemistry or biology" denotes that this is an inequality..i.e. a number greater than or equal to 30 is the number of students not majoring in C or B. Therefore you will have a range for your answer, when you start filling in your set.
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StaceyKoprince
 Post subject:
 Post Posted: Mon Sep 24, 2007 10:15 pm 
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ManhattanGMAT Staff


Posts: 6077
Location: San Francisco
Yep, GMATAttack has it - you can't fill in single numbers, you've got to fill in the range, and then carry those ranges through the calculations to get the answer.

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Stacey Koprince
Instructor
Director of Online Community
ManhattanGMAT
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