Question

In a class of 45 students, the ratio of the number of boys and girls is 4 : 5. The average score of boys in mathematics is 78. If the average score of all the students in the class in mathematics is 76, then what is the average score of girls in mathematics?
1.    73.6
2.    71.8
3.    72.4
4.    74.4

Answer 1

Correct Answer - Option 4 :    74.4

Given:

Boy : girl = 4 : 5

Calculation:

Let number of boys and girls in a class be 4a and 5a respectively.

Total score of boys = 78 × 4a

Total score of class = 76 × 9a

Total score of girls = 76 × 9a - 78 × 4a = 372a

∴ Average score of girls = 372a/5a = 74.4