Question

In a class of $100$ students there are $70$ boys whose average marks in a subject are $75$ . If the average marks of whole class is $72$ then what is the average marks of the girls?

• A. $73$
• B. $65$
• C. $68$
• D. $79$

Answer 1

The correct option is B $65$

Total students $=100$

Average marks $=72$

Total marks of the class $=72\times 100=7200$

Total marks of the boys $=70\times 75=5250$

$\Rightarrow$ Total marks of the girls$=7200=5250=1950$

$\therefore$ Average marks of the girls$=\frac{1950}{30}=65$

Hence, option $B$ is correct.