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by mmslf75 » Wed Dec 16, 2009 7:37 am
If among 20 students in a group, 5 study math, 10 study physics, and 6 study chemistry, are there any students who do not study any of the above-mentioned subjects?
1. There are no students studying all of the three subjects.
2. None of those who study math study chemistry.


OA D
Source : GMATClub Test

Can't understand why ??
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Source: — Data Sufficiency |
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by gmat_basher » Wed Dec 16, 2009 5:30 pm
Is the Answer E?

1. Insufficient,
If each student take 2 subjects, then the minimum number of students will be 15
-> 9 Math students + 1 (M+C) + 5(P+C)

2. Insufficient,
as there can be same comination as above swapped with Physics subject. with minium 15 students studying and 5 students not studying anything.
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by viju9162 » Wed Dec 16, 2009 9:41 pm
I find it complex to solve these kind of problems.

I always use the formula : N (A U B U C ) = N(A) + N(B) + N(C) - N ( A intersection B) - N ( A interesction C) - N ( B intersection C) + N ( A interesction B interesction C)..

Is there any simple formula to solve these kind of problems..

BTW, I couldn't derive the answer :(
"Native of" is used for a individual while "Native to" is used for a large group
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