Question

the average weight of 25 students of a class is 28 Kg if the average weight of all the boys is 30 kg and average weight of all the girls is 25kg then find the number of boys in the class ​

Answer 1

Given:

Average weight of 25 students of a class = 28 kg

Average weight of all the boys = 30 kg

Average weight of all the girls = 25 kg

To find:

Number of boys in the class.

Solution:

Let the number of boys be x.

Total weight of class = 25*28 = 700 kg

The total weight of class will be the sum of weights of all the boys and girls:

700 = 30x + 25(25-x)

700 = 30x + 625 - 25x

700 - 625 = 30x - 25x

75 = 5x

x = 15

Therefore the number of boys in the class should be 15.