Question

Question 11
A class consists of 50 students out of which 30 are girls. The mean of marks scored by girls in a test is 73 ( out of 100) and that of boys is 71. Determine the mean score of the whole class.

Answer 1

Given, the number of girls out of 50 students = 30
$\therefore$ The number of boys out of 50 students = 50 - 30 = 20
Now, the marks obtained by 30 girls $=30\times 73=2190$
Marks obtained by 20 boys $=20\times 71=1420$
[$\because$ mean of marks scored by girls is 73 and that of boys is 71]
$\therefore$ Mean score of the whole class
$=\frac{\text{Marks obtained by 30 girls + Marks obtained by 20 boys}}{\text{Number of girls + Number of boys}}$

$=\frac{2190+1420}{20+30}=\frac{3610}{50}=72.2$

Hence, the mean score of whole class is 72.2.