In a class of boys and girls, 60% of the students are girls. The average weight of the boys is 58 kg and that of the girls is 52 kg. What is the average weight of the whole class?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 54.4 kg
The class average is a weighted average: each group’s average counts in proportion to its share of the class.
Take 100 students: 60 girls and 40 boys
Total weight \(=40\times58+60\times52=2320+3120=5440\) kg
\(\displaystyle \text{Average}=\frac{5440}{100}=54.4\) kg
The average weight of the class is 54.4 kg, nearer the girls’ 52 kg because girls are the larger group. The plain middle value 55 kg would need equal numbers of boys and girls.