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

$A$ tub contains a mixture of two liquids $P$ and $Q$ in the ratio of $4:1$. When $10 \, L$ of the mixture is taken out and $10 \, L$ of liquid $Q$ is poured into the tub,the ratio becomes $2:3$. How many litres of liquid $P$ were contained in the tub initially?

Two varieties of sugar are mixed together in a certain ratio. The cost of the mixture per $kg$ is ₹ $0.50$ less than that of the superior and ₹ $0.75$ more than the inferior variety. The ratio in which the superior and inferior varieties of sugar have been mixed is

$8$ litres of water is added to $32$ litres of a solution containing $20 \%$ of alcohol in water. What is the approximate concentration of alcohol in the solution now? (in $\%$)

$A$ bottle full of whisky contains $50 \%$ alcohol. $A$ part of this whisky is replaced by another containing $18 \%$ alcohol and the percentage of alcohol was found to be $26 \%$. The quantity of whisky replaced is

In what ratio must sugar at $Rs. 2$ per $kg$ be mixed with sugar at $Rs. 3.50$ per $kg$ so that the mixture is worth $Rs. 2.50$ per $kg$?