The ratio after adding water — Aptitude Question
The ratio after adding water: A 45-litre mixture has milk and water in the ratio 4 : 1. If 10 litres of water is… Answer and worked solution on CodeKairo.
- Topic: Mixtures & Alligation
- Section: Quantitative Aptitude
- Difficulty: Medium
- Time target: 75 seconds
Question
A 45-litre mixture has milk and water in the ratio 4 : 1. If 10 litres of water is added, what is the new ratio?
Options
- 4 : 3
- 36 : 19
- 18 : 11
- 2 : 1
Show the answer and the worked solution
Correct answer: B. 36 : 19
Worked solution
- Milk = (4/5) × 45 = 36 L; water = 9 L.
- After adding 10 L of water: water = 19 L, milk unchanged at 36 L.
- New ratio = 36 : 19.
Answer: 36 : 19.
The idea
Only the added component changes. Compute both amounts first, adjust one, and leave the ratio unreduced if it has no common factor.
Shortcut. Milk stays 36 L and water becomes 19 L; 19 is prime and does not divide 36, so the ratio cannot reduce — only 36 : 19 fits.
Common trap. 2 : 1 — the neat ratio 36 : 19 nearly is; it would need 18 L of water, i.e. 9 L added rather than 10.