$A$ dishonest milkman professes to sell his milk at cost price but he mixes it with water and thereby gains $25 \%$. The percentage of water in the mixture is: (in $\%$)

The cost of Type $1$ rice is $Rs. 15$ per $kg$ and Type $2$ rice is $Rs. 20$ per $kg$. If both Type $1$ and Type $2$ are mixed in the ratio of $2:3$,then the price per $kg$ of the mixed variety of rice is? (in $Rs.$)

The ratio in which tea costing $Rs. 192$ per $kg$ is to be mixed with tea costing $Rs. 150$ per $kg$ so that the mixed tea,when sold for $Rs. 194.40$ per $kg$,gives a profit of $20\%$,is:

$A$ trader has $50 \text{ kg}$ of pulses,part of which he sells at $8 \%$ profit and the rest at $18 \%$ profit. He gains $14 \%$ on the whole. What is the quantity sold at $18 \%$ profit? (in $\text{kg}$)

Two vessels contain milk and water in the ratio $3:2$ and $7:3$. Find the ratio in which the contents of the two vessels have to be mixed to get a new mixture in which the ratio of milk and water is $2:1$.

Gold is $21$ times as heavy as water and copper is $11$ times as heavy as water. In what ratio should these metals be mixed so that the mixture may be $17$ times as heavy as water?