Multiple choice

In a class, there were 9 boys and some girls. In a test the mean score obtained by boys was 12 while that obtained by the girls was 14. If the overall average was 13.1, what was the total number of students in the class?

  1. 21

  2. 19

  3. 22

  4. 20
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let number of girls = g. Total score = 9×12 + g×14 = 108 + 14g. Total students = 9 + g. Average = (108 + 14g)/(9 + g) = 13.1. Solving: 108 + 14g = 117.9 + 13.1g, so 0.9g = 9.9, giving g = 11. Total students = 9 + 11 = 20.

Keep practicing — related questions