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

How many kilograms of sugar costing $Rs. 9$ per $kg$ must be mixed with $27\, kg$ of sugar costing $Rs. 7$ per $kg$ so that there may be a gain of $10\%$ by selling the mixture at $Rs. 9.24$ per $kg$?

$A$ 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?

The average monthly salary of employees,consisting of officers and workers of an organization,is ₹$3000$. The average salary of an officer is ₹$10000$ while that of a worker is ₹$2000$ per month. If there are a total of $400$ employees in the organization,find out the number of officers and workers separately.

There are two containers of equal capacity. The ratio of milk to water in the first container is $3:1$,and in the second container,it is $5:2$. If they are mixed,the ratio of milk to water in the mixture will be:

In a mixture of $75 \, litres$,the ratio of milk to water is $2:1$. The amount of water to be further added to the mixture so as to make the ratio of milk to water $1:2$ will be (in $litres$):