Question

From a school 90 boys and 30 girls appeared for a public examination. The mean mark of boys is found to be $45\%$ whereas the mean mark of girls is $70\%$. What is the average marks $\%$ of the school?

• A. $61.50\%$
• B. $51.25\%$
• C. $40.50\%$
• D. $51.52\%$

Answer 1

The correct option is B

$51.25\%$

Number of boys in the school = 90
Mean marks of boys $=45\%$
Total marks of 90 boys $=90\times 45=4050$
Number of girls in the school = 30
Mean marks of girls $=70\%$
$\therefore$ Total marks of 30 girls $=30\times 70=2100$
Total marks secured by 90 boys and 30 girls
= 4050 + 2100 = 6150
Number of boys and girls who have appeared for exam from the school
= 90 + 30 = 120
$\therefore$ Average marks $\%$ of school
$=\frac{6150}{120}=51.25\%$