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

$\begin {array} {1 1} (A)\;73 & \quad (B)\;65 \\ (C)\;68 & \quad (D)\;74 \end {array}$

For 70 students total marks = $75 \times 70$
$= 5250$