Question

There are 100 students in a class. 40 of them are girls. The average marks of the boys in science is 75% and that of the girls is 65%. Find the average marks of the class in science.

Answer 1

Let the total number of boys in the class be B.

Total number of students = 100
Number of girls = 40
Number of boys = B

Therefore, B + 40 = 100

B = 60

Let the total marks scored by all the boys in science be X.

Total marks scored by the boys = B × 75% = 0.75B
Total marks scored by the girls = 40 × 65% = 26

Total marks scored by the entire class = X + 26

The average marks of the class in science = (Total marks scored by the entire class) / (Total number of students)

= (X + 26) / 100

But X = 0.75B

Therefore, the average marks of the class in science = (0.75B + 26) / 100

= (0.75 × 60 + 26) / 100

= 56.5%

Therefore, the average marks of the class in science is 56.5%.