Question

There are 50 students in a class, of which 40 are boys. The average weight of the class is 44 kg and that of girls is 40 kg. Find the average weight of the boys.

Answer 1

Total students in the class = 50
Number of boys = 40
∴ Number of girls = (50 - 40) = 10
Average weight of students in the class = 44 kg
Average weight of girls in the class = 40 kg
Sum of the weights of girls in the class = (40 ×10) kg = 400 kg
Thus, we have:

$\text{The average weight of students in the class}=\frac{\text{Total weight of girls in the class+Total weight of boys in the class}}{\text{Total number of students in the class}}\Rightarrow 44=\frac{400+\text{Total weight of boys in the class}}{50}\Rightarrow \text{Total weight of boys in the class}+400=2200\Rightarrow \text{Total weight of boys in the class}=1800kg\text{The average weight of boys}=\frac{1800}{40}=45kg$