UPSC CDS 2 2018 Math Paper

Percentage of students failed in English = n(E) = 50.
Percentage of students failed in Hindi = n(H) = 40.
Percentage of students failed in both English and Hindi = n(E∩H) = 15.
We know, n(E∪H) = n(E) + n(H) – (E∩H)Percentage of candidates failed in at least one subject =50+40–15=75%.
Percentage of candidates passed in both the subjects = 100%–75%=25%.