Subject: mathqa
Question: students of 3 different classes appeared in common examination . pass average of 10 students of first class was 45 % , pass average of 15 students of second class was 60 % and pass average of 25 students of third class was 80 % then what will be the pass average of all students of 3 classes ?
Option: 
A: 74 %
B: none
C: 67 %
D: 72 %
Answer: C