In a Physics test, the average marks of girls in a class is 40. If the average marks of the first 20 girls is 50 and that of the remaining girls is 20, then the total number of girls in the class is:

Question

Accepted Answer

Let the total number of girls in the class be $$ x $$.

The total marks for all girls can be expressed as:  
$$
	ext{Total Marks} = 	ext{Average Marks} 	imes 	ext{Total Number of Girls} = 40x.
$$

The marks for the first 20 girls are:  
$$
20 	imes 50 = 1000.
$$

The marks for the remaining $$ x - 20 $$ girls are:  
$$
(x - 20) 	imes 20.
$$

According to the question, the total marks for all girls is:  
$$
1000 + (x - 20) 	imes 20 = 40x.
$$

Simplify this equation:  
$$
1000 + 20x - 400 = 40x.
$$  
$$
600 = 20x.
$$  
$$
x = 30.
$$

Thus, the total number of girls in the class is **30**, which corresponds to option **(a)**.

Answer

Answer

Answer