A mixture of milk and water contains 80% milk. How many litres of water must be added to 50 litres of this mixture to raise the percentage of water to 25%?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → \(3\frac{1}{3}\)
When only water is added, the quantity of milk does not change. Once water is 25%, milk is 75% of the new mixture, which fixes the new volume.
Milk \(=80\%\) of 50 \(=40\) litres
In the new mixture milk \(=100\%-25\%=75\%\)
New volume \(\displaystyle =\frac{40}{0.75}=\frac{160}{3}=53\frac{1}{3}\) litres
Water added \(\displaystyle =53\frac{1}{3}-50=3\frac{1}{3}\) litres
\(3\frac{1}{3}\) litres of water must be added.