Find the ratio in which rice at $Rs. 7.20$ per $kg$ should be mixed with rice at $Rs. 5.70$ per $kg$ to produce a mixture worth $Rs. 6.30$ per $kg$.

In what ratio should tea at ₹ $240$ per $kg$ be mixed with tea at ₹ $280$ per $kg$ so that on selling the mixture at ₹ $324$ per $kg$ there is a profit of $20 \%$?

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

In what ratio must a grocer mix two varieties of pulses costing ₹ $15$ and ₹ $20$ per $kg$ respectively so as to get a mixture worth ₹ $16.5/kg$?

Two casks of $48$ $litres$ and $42$ $litres$ are filled with mixtures of wine and water,the proportions in the two casks being respectively $13:7$ and $18:17$. If the contents of the two casks are mixed,and $20$ $litres$ of water is added to the whole,what will be the proportion of wine to water in the resultant mixture?