In what ratio must oil at $Rs. 62$ per $kg$ be mixed with oil at $Rs. 72$ per $kg$ so that the mixture is worth $Rs. 64.50$ per $kg$?

In a $120$ $litre$ mixture of milk and water,water is only $25 \%$. The milkman sold $20$ $litre$ of this mixture and then added $16.2$ $litre$ of pure milk and $3.8$ $litre$ of pure water to the remaining mixture. What is the percentage of water in the final mixture (in $\%$)?

In what ratio must water be mixed with milk to gain $16 \%$ on selling the mixture at cost price?

$A$ person has a chemical of ₹ $25$ per litre. In what ratio should water be mixed in that chemical,so that after selling the mixture at ₹ $20$ per litre,he may get a profit of $25 \%$?

$A$ mixture of $48$ litre of milk and water contains $10 \%$ of water. How much water must be added to make $20 \%$ water in the new mixture?

$A$ mixture contains $80 \%$ acid and the rest water. The part of the mixture that should be removed and replaced by the same amount of water to make the ratio of acid and water $4:3$ is