UPSC NDA Math Model Paper 2

Let A be the set of students who read "Hitavad" and B the set of students who read "Hindustan".
From the given information:
n(A ⋃ B) = 50 - 10 = 40.
n(A) = 30.
n(B) = 35.
By using n(A ⋃ B) = n(A) + n(B) - n(A ⋂ B), we get:
40 = 30 + 35 - n(A ⋂ B)
⇒ n(A ⋂ B) = 25.
∴ The number of students who read both "Hitavad" and "Hindustan" newpapers is n(A ⋂ B) = 25.