A milkman mixes 30 liters of water and 70 liters of milk. After selling $\frac{1}{4}$ part of this mixture, he adds as much water to the remaining mixture as he sold. What will be the ratio of water to milk in the final mixture?

Explanation

Total mixture = 100 liters Water : Milk = 30 : 70 = 3 : 7 $\frac{1}{4}$ part remaining mixture after sale = $100 - 25 = 75$ L. $\therefore$ The quantity of milk in 75 liters of mixture = $75 \times \frac{7}{10}$ = $\frac{105}{2}$ L. The quantity of water in 75 liters of mixture = $75 \times \frac{3}{10}$ = $\frac{45}{2}$ L. Total water in the mixture after adding 25 liters of water = $\frac{45}{2} + 25 = \frac{95}{2}$ L. $\therefore$ Required ratio = $\frac{\frac{95}{2}}{\frac{105}{2}}$ = 95 : 105 = 19 : 21