The milk and water in a mixture are in the ratio 7 : 5. When 15 litres of water are added to it, the ratio of milk and water in the new mixture becomes 7 : 8. The total quantity of water in the new mixture is

Question: The milk and water in a mixture are in the ratio 7 : 5. When 15 litres of water are added to it, the ratio of milk and water in the new mixture becomes 7 : 8. The total quantity of water in the new mixture is

Solution:
Let the quantity of milk in the mixture = 7x litres and that of water = 5x litres.
ATQ,
7x/(5x + 15) = 7/8
⇒ 56x = 35x + 105
⇒ 56 x - 35 x = 105
⇒ 21x = 105
⇒ x = 5

Required quantity of water = (5x + 15) litres
= 5 × 5 + 15
= 40 litres