One replacement — Mixtures & Alligation Aptitude Question
One replacement: From 50 litres of milk, 10 litres is removed and replaced with water. How much milk remains? Answer and worked solution on CodeKairo.
- Topic: Mixtures & Alligation
- Section: Quantitative Aptitude
- Difficulty: Easy
- Time target: 45 seconds
Question
From 50 litres of milk, 10 litres is removed and replaced with water. How much milk remains?
Options
- 35 L
- 38 L
- 40 L
- 45 L
Show the answer and the worked solution
Correct answer: C. 40 L
Worked solution
- Fraction remaining = 1 − 10/50 = 0.8.
- Milk left = 50 × 0.8 = 40 L.
Answer: 40 L.
The idea
A single replacement is a plain subtraction, but writing it as a fraction prepares you for the repeated case.
Shortcut. The first draw is pure milk, so exactly 10 L of milk leaves the can: 50 − 10 = 40 L.
Common trap. "45 L" — treating the 10 L as 10% of the milk (50 × 0.9); it is 10 of 50 litres, one fifth.