$A$ mixture of $40$ $litres$ of milk and water contains $10 \%$ water. How much water must be added to make $20 \%$ water in the new mixture? (in $Liters$)

How much water should be added to $14$ litres of milk worth ₹ $5.40$ a litre so that the value of the mixture may be ₹ $4.20$ a litre? (in litres)

In what ratio must a grocer mix two varieties of tea worth $Rs. 60$ per $kg$ and $Rs. 65$ per $kg$ so that by selling the mixture at $Rs. 68.20$ per $kg$ he may gain $10\%$?

Three bottles of equal capacity contain mixtures of milk and water in the ratios $2:5$,$3:4$,and $4:5$ respectively. These three bottles are emptied into a large bottle. What will be the ratio of milk and water respectively in the large bottle?

$A$ man has given ₹ $300000$ as a loan. He lent some of his capital to Ajay at an interest rate of $20 \%$ per annum and the rest to Ramesh at an interest rate of $12 \%$ per annum. At the end of one year,he received $17 \%$ of his total capital as interest. How much did he lend to Ajay? (in ₹)

If $5 \ kg$ of potato costing $Rs. 5$ per $kg$ and $3 \ kg$ of potato costing $Rs. 4$ per $kg$ are mixed,find the average cost of the mixture per $kg$?