Ratio of water and milk in a container is 2 : 3. If 40 liter mixture removed from the container and same quantity of milk is added to it then the ratio of water to milk becomes 1 : 4. Find the initial quantity of mixture?

From the given data,

let the initial quantity of the mixture = 5x

Then,

$$\begin{gathered} 2 x - 16 3 x - 24 + 40 = 1 4 \\ 8 x - 64 = 3 x + 16 \\ 5 x = 80 \\ x = 16 lit \end{gathered}$$

Then the initial quantity of the mixture = 5x = 5 x 16 = 80 lit.