Aluminium is extracted from the ore Bauxite, which is impure Aluminium oxide. $1 \mathrm{tonne} \left(1000 \mathrm{kg}\right)$ of the ore was found to have this composition: 

Aluminium oxide $\left(825 \mathrm{kg}\right)$, Iron $\left(\mathrm{III}\right)$ oxide $\left(100 \mathrm{kg}\right)$ and sand $\left(75 \mathrm{kg}\right)$.

$1 \text{tonne}$ of ore gives $437 \mathrm{kg}$ of Aluminium. How much aluminium will be obtained from $5 \mathrm{tonnes}$ of the ore?

Aluminium oxide $\left(825 \mathrm{kg}\right)$, Iron $\left(\mathrm{III}\right)$ oxide $\left(100 \mathrm{kg}\right)$ and sand $\left(75 \mathrm{kg}\right)$

$1 \mathrm{tonne}$ of ore gives $437 \mathrm{kg}$ of Aluminium. What mass of sand is in this $5 \mathrm{tonnes}$?

Aluminium oxide $\left(825 \mathrm{kg}\right)$, Iron $\left(\mathrm{III}\right)$ oxide $\left(100 \mathrm{kg}\right)$ and sand $\left(75 \mathrm{kg}\right)$.

What will be the percentage of Aluminium oxide in the ore, if all the Iron $\left(\mathrm{III}\right)$ oxide is removed, leaving only the Aluminium oxide and sand?