More men, fewer days — Ratio & Proportion Aptitude Question
More men, fewer days: 12 men can build a wall in 20 days. Working at the same rate, how many days will 15 men take? Answer and worked solution on CodeKairo.
- Topic: Ratio & Proportion
- Section: Quantitative Aptitude
- Difficulty: Easy
- Time target: 40 seconds
Question
12 men can build a wall in 20 days. Working at the same rate, how many days will 15 men take?
Options
- 15
- 16
- 18
- 25
Show the answer and the worked solution
Correct answer: B. 16
Worked solution
- Total work = 12 × 20 = 240 man-days.
- Days for 15 men = 240 ÷ 15 = 16.
Answer: 16.
The idea
For inverse variation, keep the product constant (man-days here). Direct variation keeps the ratio constant. Decide which before writing anything.
Shortcut. Men rise by 15/12 = 5/4, so days fall by 4/5: 20 × 4/5 = 16.
Common trap. 25 — treating it as direct variation (20 × 15/12); more men need fewer days, not more.