In a class of 55 students there are 34 girls. The average weight of these girls is 51Kg and average weight of the full class is 55.2kgs. What is the average weight of the boys of the class?
- A62
- B59.4
- C56.8
- D60
Solution & Step-by-step Explanation
Given:
Total students = 55
Number of girls = 34
Number of boys = 55−34=21
Average weight of girls = 51kg
Average weight of full class = 55.2kg
Let the average weight of the boys be xkg.
Using the weighted average formula:
Total Weight=(Number of girls×Average weight of girls)+(Number of boys×Average weight of boys)
Total Weight=55×55.2=3036kg
Sum of weight of girls:
34×51=1734kg
Sum of weight of boys:
21×x=3036−1734
21x=1302
x=
21
1302
=62kg
Total students = 55
Number of girls = 34
Number of boys = 55−34=21
Average weight of girls = 51kg
Average weight of full class = 55.2kg
Let the average weight of the boys be xkg.
Using the weighted average formula:
Total Weight=(Number of girls×Average weight of girls)+(Number of boys×Average weight of boys)
Total Weight=55×55.2=3036kg
Sum of weight of girls:
34×51=1734kg
Sum of weight of boys:
21×x=3036−1734
21x=1302
x=
21
1302
=62kg