Question

in a class of 60 students,40% are girls. the average weight of boys is 62kg and that of girls is 55kg. what is the average weight of whole class?​

Answer 1

Answer:

Let the no. of boys = x

no. of girls = 60-x

A/Q,

mean weight of boys = 50 kg

    Total weight  of boys ÷ x = 50  

⇒ total weight of boys = 50x

 

And,

mean weight of girls = 30 kg

   Total weight  of girls ÷ (60-x) = 30  

⇒  Total weight of girls = 30(60-x) =1800 - 30x

now,

mean weight of 60 students = 40 kg

    (Weight of girls + Weight of boys) ÷  total no. of students = 40

⇒   (1800 -30x + 50x) ÷ 60 =40

⇒   1800 + 20x =40 ×60

⇒    20x = 2400 - 1800

⇒    20x = 600

          x = 600/20 = 30

Therefore total no. of boys = 30

and total no of girls = 60 - 30 = 30

Therefore,

No. of Boys =30

No. of Girls = 30