In a class of 56 students there are 21 girls. The average weight of these girls is 56kg and the average weight of the full class is 62.875kgs. What is the average weight of the boys of the class?
- A69.75 kg
- B72.5 kg
- C67 kg
- D65 kg
Solution & Step-by-step Explanation
Total number of students = 56
Number of girls = 21
Number of boys = 56−21=35
Let the average weight of the boys be xkg.
Using the concept of total weight:
Total weight of class=Total weight of girls+Total weight of boys
56×62.875=21×56+35×x
To simplify, divide the entire equation by 7:
8×62.875=3×56+5×x
503=168+5x
5x=503−168
5x=335
x=
5
335
=67kg
Thus, the average weight of the boys is 67kg.
Number of girls = 21
Number of boys = 56−21=35
Let the average weight of the boys be xkg.
Using the concept of total weight:
Total weight of class=Total weight of girls+Total weight of boys
56×62.875=21×56+35×x
To simplify, divide the entire equation by 7:
8×62.875=3×56+5×x
503=168+5x
5x=503−168
5x=335
x=
5
335
=67kg
Thus, the average weight of the boys is 67kg.