In a class of 80 students (boys and girls) there are 60% girls. The average weight of the boys is 58 kg and that of the girls is 52 kg. What is the average weight(in kg) of the whole class?

54.4

Ratio of number of girls to boys = 3 : 2

Number of girls = \(\frac{3}{5}\)  × 80 = 48

& number of boys = 80 - 48 =  32

Total weight = 48  × 52 + 32  × 58 = 2496 + 1856 = 4352

Average weight of whole class = \(\frac{4352}{80}\) = 54.4 kg