Question

A class has 30 boys and 20 girls. The average age of

boys is 11 yrs and girls 12 What is the
average age of the whole class."
​

Answer 1

Given:

A class has 30 boys and 20 girls.

The average age of boys and girls is 11 and 12 respectively.

To Find:

The average age of the whole class.

Solution:

Boys = No. of boys × Age

Boys = 30 × 11 = 330

Girls = No. of girls × Age

Girls = 20 × 12 = 240

Average Age = Boys + Girls / Total no. of boys and girls

Average Age = 330 + 240 / 50

Average Age = 570 / 50

Average Age = 11.4

Answer:

Average age of of the whole class is 11.4 .

Answer 2

x = total age of boys

x / 30 = 11yrs

Multiply both sides by 30

x = 330

y = total age of girls

y / 20 = 12

Multiply both sides by 20

y = 240

(240 + 330) / 50 = 11.4 yrs

The average age of the whole class = 11.4 years.