A dishonest milkman mixes milk to mineral water in the ratio of 5: 3. He sells the mixture at the cost price of milk and earns a profit of 20%. If the price of mineral water is Rs. 20 per litre, then the price of one litre milk is how much percentage more than that of one litre mineral water?

Let milk price be M and water price be W = Rs. 20/litre. Mixture ratio is 5:3. For every 8 litres of mixture, 5 litres are milk (cost 5M) and 3 litres are water (cost 3W = 60). Cost price of 8 litres = 5M + 60. Selling price of 8 litres = 8M (selling at milk price). Profit = 20%, so 8M = 1.2 × (5M + 60). Solving: 8M = 6M + 72, so 2M = 72, M = 36. Water price = 20. Difference = 36 - 20 = 16. Percentage more = (16/20) × 100 = 80%.