In a class of 50 students, 30% are girls. The average weight of the whole class is 45 kg and the average weight of the girls is 31 kg. What is the average weight of the boys?

53 kg 51 kg 55 kg 65 kg

51 kg

Total no. of students = 50 30% = \(\frac{3}{10}\) Ratio of no. of boys to girls = 7 : 3