Question

In a competitive exam 50 students passed in English. 60 students passed in Mathematics. 40 students passed in both the subjects. None of them fail in both the subjects. Find the number of students who passed at least in one of the subjects ?

Answer 1

Let A be the set of students who passed in English, and B be the set of students who passed in Mathematics.

We have,

n(A) = 50, n(B) = 60, $n(A\cap B)=40$

Since,

$n(A\cup B)=n\left(A\right)+n\left(B\right)-n(A\cap B)=50+60-40$

$n(A\cup B)=70$

So, the number of students who passed at least in one of the subjects is 70.