$A$ drum contains $80$ $litres$ of ethanol. $20$ $litres$ of this liquid is removed and replaced with water. $20$ $litres$ of this mixture is again removed and replaced with water. How much water (in $litres$) is present in this drum now?

There are two containers of equal capacity. The ratio of milk to water in the first container is $3:1$,and in the second container is $5:2$. If they are mixed together,then the ratio of milk to water in the mixture will be:

Three glasses of capacity $2 \, L$,$5 \, L$,and $9 \, L$ contain mixtures of milk and water with milk concentrations of $90 \%$,$80 \%$,and $70 \%$ respectively. The contents of the three glasses are emptied into a large vessel. Find the ratio of milk to water in the resultant mixture.

Nikita bought $30 \text{ kg}$ of wheat at the rate of $Rs. 9.50$ per $\text{kg}$ and $40 \text{ kg}$ of wheat at the rate of $Rs. 8.50$ per $\text{kg}$ and mixed them. She sold the mixture at the rate of $Rs. 8.90$ per $\text{kg}$. Her total profit or loss in the transaction was:

In a laboratory,two bottles contain a mixture of acid and water in the ratio $2:5$ in the first bottle and $7:3$ in the second. The ratio in which the contents of these two bottles should be mixed such that the new mixture has acid and water in the ratio $2:3$ is

Two vessels contain milk and water in the ratio $3:2$ and $7:3$. Find the ratio in which the contents of the two vessels have to be mixed to get a new mixture in which the ratio of milk and water is $2:1$.