$A$ 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?

In a zoo,there are rabbits and pigeons. If the heads are counted,there are $200$ and if legs are counted,there are $580$. How many pigeons are there?

$A$ jar contained a mixture of two liquids $A$ and $B$ in the ratio $3 : 2.$ When $5$ litres of the mixture was taken out and $5$ litres of liquid $B$ was poured in the jar,this ratio became $2 : 3.$ The quantity of liquid $A$ contained in the jar initially was (in litres).

$A$ can contains a mixture of two liquids $A$ and $B$ in the ratio $4:7$. When $6 \text{ litres}$ of the mixture are drawn off and the can is filled with liquid $B$,the ratio of $A$ and $B$ becomes $3:7$. How many litres of liquid $A$ were contained in the can initially?

The ratio of milk and water in mixtures of four containers are $5:3$,$2:1$,$3:2$,and $7:4$,respectively. In which container is the quantity of milk,relative to water,the minimum?

How many $Kg$ of tea,worth ₹ $25$ per $Kg$,must be blended with $30 \ Kg$ of tea worth ₹ $30$ per $Kg$,so that by selling the blended variety at ₹ $30$ per $Kg$ there should be a gain of $10 \%$?