Quantitative Aptitude :: Problems on Numbers - Discussion

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Explanation:
If we assume exactly 30 students are not majoring in any subject then the students who take atleast one subject = 200 - 30 = 170
We know that n(A?B) = n(A) + n(B) - n(A?B)
=> 170 = 130 + 150 - n(A?B)
Solving we get n(A?B) = 110.
i.e., Students who can take both subjects are 110
But If more than 30 students are not taking any subject, what can be the maximum number of students who can take both the subjects?
As there are 130 students are majoring in chemistry, assume these students are taking biology also. So maximum students who can take both the subjects is 130

So the number of students who can take both subjects can be any number from 110 to 130