Diluting a sugar solution — Aptitude Question
Diluting a sugar solution: 40 litres of a solution is 25% sugar. How much water must be added to reduce it to 20%… Answer and worked solution on CodeKairo.
- Topic: Mixtures & Alligation
- Section: Quantitative Aptitude
- Difficulty: Medium
- Time target: 75 seconds
Question
40 litres of a solution is 25% sugar. How much water must be added to reduce it to 20% sugar?
Options
- 8 L
- 10 L
- 12 L
- 15 L
Show the answer and the worked solution
Correct answer: B. 10 L
Worked solution
- Sugar = 25% of 40 = 10 L, unchanged.
- New total = 10 ÷ 0.20 = 50 L.
- Water added = 50 − 40 = 10 L.
Answer: 10 L.
The idea
Dilution keeps the solute constant. Divide it by the target concentration for the new total, then subtract the old volume.
Shortcut. With the sugar fixed, volume is inversely proportional to strength: 40 × 25/20 = 50 L, so 10 L of water goes in.
Common trap. "8 L" — measuring the 5-point drop against the old strength, 40 × 5/25 = 8; it must be measured against the new 20%: 40 × 5/20 = 10.