Adding water to a milk mixture — Aptitude Question
Adding water to a milk mixture: A 60-litre mixture contains milk and water in the ratio 2 : 1. Answer and worked solution on CodeKairo.
- Topic: Mixtures & Alligation
- Section: Quantitative Aptitude
- Difficulty: Easy
- Time target: 45 seconds
Question
A 60-litre mixture contains milk and water in the ratio 2 : 1. How much water must be added to make the ratio 1 : 1?
Options
- 10 L
- 15 L
- 20 L
- 30 L
Show the answer and the worked solution
Correct answer: C. 20 L
Worked solution
- Milk = 2/3 × 60 = 40 L; water = 20 L.
- For 1 : 1, water must equal milk = 40 L.
- Add 40 − 20 = 20 L.
Answer: 20 L.
The idea
Anchor on the component that does not change (milk) and work out what the other must become. Never re-derive both.
Shortcut. In parts, 2 : 1 must become 2 : 2, so add one more part — and one part is 60 ÷ 3 = 20 L.
Common trap. 10 L — keeping the total at 60 L and aiming for 30 L each (30 − 20); adding water raises the total, and the 40 L of milk does not change.