Question

A class consisting of 25 girls and 15 boys . If the average weight of girls is 28 kg and the average weight of boys is 32 kg,then find the average weight of students of the whole class.

Answer 1

Average weight of 25 girls is 28kg.

So , Total weight of 25 girls will be =
No. of girls × Average = 25 × 28 = 700kg.

Average weight of 15 boys is 32 boys is 32 kg.

So, total weight of boys will be =
No. of boys × Average = 15×32 = 480kg

Total number of students in class =

No of boys + No of girls
= 15+25
= 40

Total weight of all students =

Total weight of girls + Total weight of boys
= 700 + 480 = 1180kg

Average weight of all students =

Total weight / Number of student
= 1180/40
= 29.5 kg

Answer → Average weight of all students is 29.5 kg

______________________________

Answer 2

combined mean = n1 x1 + n2x2
                                 n1 + n2
girls
n1 = 25
x1 = 28

boys
n2 =15
x2 = 32

substituting in the given formula we get

 combined mean  = 25 x 28  + 15 x 32
                                      25 + 15

 = 700 + 480
          40

= 29.5

Average weight of all students is 29.5 kg