Chocolates at $Rs. 12.00$ per dozen are mixed with chocolates at $Rs. 10.00$ per dozen in the ratio $3:5$. Find the price per dozen of the mixture (in $Rs.$).

$A$ 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 $Liters$)

An amount of ₹ $70,000$ was lent at $6 \%$ per annum and the remaining at $4 \%$ per annum. If the total simple interest from both the fractions in $5 \text{ years}$ was ₹ $16,000$,the sum lent at $6 \%$ per annum was (in ₹). (in $,000$)

$300$ $grams$ of sugar solution contains $40 \%$ sugar. How much sugar should be added to make the concentration $50 \%$ in the solution? (in $grams$)

Milk and water are mixed in vessel $A$ in the ratio of $5:2$ and in vessel $B$ in the ratio of $8:5$. In what ratio should quantities be taken from the two vessels so as to form a mixture in which milk and water will be in the ratio of $9:4$?

$A$ can contains a mixture of two liquids $A$ and $B$ in the ratio $7:5$. When $9\,L$ of mixture is drained off and the can is filled with $B$,the ratio of $A$ and $B$ becomes $7:9$. How many litres of liquid $A$ was contained by the can initially?