How many students are taking either math or history? (1) In a certain

Question

How many students are taking either math or history?

(1) In a certain school, 20 students are taking math and 10 are taking history.

(2) 7 are taking both.

gmatophobia · Answer

We can use the concept of overlapping set to solve this question.

The solution is depicted in the attached image.

Option C

kienbn932 · Answer

I think it should be A
"Either" can mean taking just 1 subject or both subjects

SaquibHGMATWhiz · Answer

Hey  kienbn932  ,

We are asked the number of students taking either maths or history 
 This means we are asked the value of  n(M\cup H)

According to  statement 1 ,  n(M)=20  and  n(H)=10  which is no sufficient to get the answer 
 Accordign to  statement 2 ,  n(M \cap H)=7

Upon combining, we can say  n(M\cup H)=n(M)+n(H)-n(M \cap H)=20+10-7=23

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