In an examination, 60% of candidates passed in English and 70% of candidates passed in Mamatics, but 20% failed in both subjects. If 2500 candidates passed in both subjects, number of candidates who appeared at examination was :

Candidates failed in English
= (100 - 60)%
= 40%
Candidate failed in Mathematics
= (100 - 70)%
= 30%
20% Candidate fail in Both.
Candidate only fail in English = 40 - 20 = 20%
Candidate only fail in Mathematics = 30 - 20 = 10%
Students passed in both subjects
= 100 - (20% Candidate fail in Both + Candidate only fail in English + Candidate only fail in Mathematics)
= 100 - (20 + 20 + 10)
= 50%
50% of students = 2500
Total students = $$\frac{{2500}}{{50}} \times 100$$
                      = 5000