Q. In a class of 100 students there are 70 boys whose average marks in a subject are 75. If the average marks of the complete class is 72, then what is the average of the girls?
A) 73
B) 65
C) 68
D) 74
Explanation
(b)
Total number of students=100
Average marks of the class=72
Total marks of the class $= 72 \times 100 = 7200$
And total marks of the boys $= 70 \times 75 = 5250$
So, total marks of the girls=$7200 - 5250 = 1950$
Hence, average of girls $= \frac{1950}{30} = 65$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.