In a class of 60 students there are 30 girls. The average weight of these girls is 58kg and average weight of the full class is 63kg. What is the average weight of the boys of the class?

Total number of students in the class = 60
Number of girls = 30

Therefore, number of boys = 60−30=30

The average weight of the entire class is 63kg.

Total weight of the class=60×63=3780kg
The average weight of the girls is 58kg.

Total weight of the girls=30×58=1740kg
Now, find the total weight of the boys:

Total weight of the boys=Total weight of the class−Total weight of the girls
Total weight of the boys=3780−1740=2040kg
Calculate the average weight of the boys:

Average weight of the boys=
Number of boys
Total weight of the boys
​

Average weight of the boys=
30
2040
​
=68kg