In a class, 60% of students passed in English and 70% passed in Mathematics. If 20% failed in both subjects, what percentage passed in both?

Explanation

Total students = 100%. Percentage passing in at least one subject = 100% – 20% = 80%. n(E U M) = n(E) + n(M) – n(E n M) => 80 = 60 + 70 – n(E n M) => n(E n M) = 130 – 80 = 50%.