Statistics problem related to mean

Question

The mean of marks in pharmaceutical mathematics of 100 students in B.Pharmacy class was 72. The mean marks of boys was 75, while their number was 70. Find the mean marks of girls in the class.

Answer 1

following the answer of iamwhoiam , $$Total~marks~of~boys=75\times 70=5250$$$$Total~marks~of~class=100\times 72=7200$$$$So,total~marks~of~girls=1950$$ and you know total girls are $30$$$So~mean~marks~of~girls=\frac{1950}{30}=65$$All calculations are done by using $$Total~marks=Average~marks\times No.~of~students$$as mentioned in answer of iamwhoiam

Answer 2

Hint:

The total marks of a subset of students is calculated as follows:

$Total\ marks = Average\ marks\ *\ No.\ of\ students$

Set the unknown quantity to a variable $x$, and form your equations by using the fact that the sum of the total marks of the boys and the total marks of the girls is the total marks obtained by the class.