Question

There 40 students in a chemistry class and 60 students in physics class. Find the number of students which are

either in Physics class or Chemistry class in the cases.

(i) the two classes meet at the same hour.

(ii) the two classes meet at different hours and 20 students are enrolled in both the subjects.
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Answer 1

Answer:

Let A be the set of students in chemistry class and B be the set of students in physics class. It is given that n(A)=40 and n(B)=60. If two classes meet at different timings then there can be some student sitting in both the classes. =40+60−20=80.