In what proportion must a grocer mix sugar at ₹ $12$ per $kg$ and ₹ $7$ per $kg$ so as to make a mixture worth ₹ $8$ per $kg$?

How much tea at $Rs. 4$ a $kg$ should be added to $15 \, kg$ of tea at $Rs. 10$ per $kg$ so that the mixture is worth $Rs. 6.50$ a $kg$? (in $kg$)

There are two vessels $A$ and $B.$ Vessel $A$ contains $40$ $litres$ of pure milk and vessel $B$ contains $22$ $litres$ of pure water. From vessel $A,$ $8$ $litres$ of milk is taken out and poured into vessel $B.$ Then,$6$ $litres$ of the mixture (milk and water) is taken out from vessel $B$ and poured into vessel $A.$ What is the ratio of the quantity of pure milk in vessel $A$ to the quantity of pure water in vessel $B\,?$

$A$ 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 $25 \%$?

In what ratio should coffee powder costing ₹ $2500$ per $kg$ be mixed with coffee powder costing ₹ $1500$ per $kg$ so that the cost of the mixture is ₹ $2250$ per $kg$?

$200$ litres of mixture contains $15 \%$ water and the rest is milk. The amount of milk that must be added so that the resulting mixture contains $87.5 \%$ milk is..........$Litre$