A mixture contains milk and water in the ratio 5:2. If 4 litres of water is added, the ratio becomes 5:4. Find the initial quantity of milk in the mixture.

माना दूध = 5x, पानी = 2x। नया पानी = 2x + 4। अतः, 5x / (2x + 4) = 5/4 => 20x = 10x + 20 => 10x = 20 => x = 2। दूध = 5 * 2 = 10 लीटर।