Multiple choice

In a mixture of milk and water, water is 30%. When 10 litre mixture is taken out and 15 litre water is added, water becomes 40%. Find initial quantity of mixture?

  1. 80 litre

  2. 75 litre

  3. 90 litre

  4. 100 litre

  5. 105 litre

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Initial mixture has 30% water. 10 litres removed means 3 litres water removed. Initial milk = 70% of M = 0.7M, water = 0.3M. After removal: milk = 0.7M - 7, water = 0.3M - 3. After adding 15 litres water: water = 0.3M + 12, total = M + 5. New percentage: (0.3M + 12)/(M + 5) = 40% = 0.4. Solving: 0.3M + 12 = 0.4M + 2, so 0.1M = 10, M = 100 litres.