The ratio of milk and water in a solution is 20 : 7 and after adding 5 liters of water in it the ratio of milk and water becomes 5 : 3, then find the final amount of water in the final solution.

Question: The ratio of milk and water in a solution is 20 : 7 and after adding 5 liters of water in it the ratio of milk and water becomes 5 : 3, then find the final amount of water in the final solution.

Solution:
Let the initial amount of milk be 20x liters and the amount of water 7x liters.

Ratio of milk and water after adding 5 liters = 20x/(7x + 5) = 5/3
⇒ 60x = 35x + 25
⇒ 25x = 25
∴ x = 1

∴ Final amount of water in solution = 7x + 5 = 7 + 5 = 12 liters.