Question

The mean marks got by $300$ students in the subject of statistics was $45$. The mean of top $100$ of them was found to be $70$ and the mean of last $100$ was known to be $20$, then the mean of remaining $100$ students is

Answer 1

The mean of remaining $100$ students
$=\frac{(300\times 45)-(70\times 100)-(20\times 100)}{100}=45$