Question

The mean weight of 150 students in a class is 60kg.The mean weight of boys in the class is 70kg.And that of the girls is 55kg.Find the number of boys and number of girls.

Please Answer

Answer 1

let the no of boys be x

so no. of girls=150-x

According to question

w1+w2+w3..............w150=60×150=9000kg...(1)

now weight of boys=70x kg.........(2)

&weight of girls=55(150-x)=8250-55x kg..(3)

using 1,2 &3

70x+8250-55x=9000
15x=750
x=50

So no of boys=50
no of girls=100