Jean drinks a quarter of a litre of his mother's orange juice, for her to not see, he replaces the amount he drank with water. Later his brother does the same thing. What is the proportion of water to juice after the last mixing?
After Jean drinks a quarter of a liter of orange juice and replaces it with water, the proportion of water to juice is 1:3 (0.25 liters of water and 0.75 liters of juice).
When his brother does the same thing, there is another 0.25 liters of water added, making the total amount of water 0.25 + 0.25 = 0.5 liters.
The total amount of juice remains the same at 0.75 liters.
Therefore, the proportion of water to juice after the last mixing is 0.5:0.75, which simplifies to 2:3.