Multiple choice

The average of marks scored by the students of a class is 68. The average of marks of the girls in the class is 80 and that of boys is 60. What is the percentage of boys in the class?

  1. 40%

  2. 60%

  3. 65%

  4. 70%
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let B boys and G girls with average scores 60 and 80. Overall average is (60B + 80G) / (B + G) = 68. Solving: 60B + 80G = 68B + 68G, giving 12G = 8B, so G/B = 2/3. Therefore B/(B+G) = 3/5 = 60%. This uses weighted averages where the overall score is between the two subgroup averages.

Keep practicing — related questions