Fewer days, more men — Ratio & Proportion Aptitude Question
Fewer days, more men: 15 men can complete a piece of work in 20 days. How many men are needed to finish it in 12… Answer and worked solution on CodeKairo.
- Topic: Ratio & Proportion
- Section: Quantitative Aptitude
- Difficulty: Easy
- Time target: 45 seconds
Question
15 men can complete a piece of work in 20 days. How many men are needed to finish it in 12 days?
Options
- 18
- 20
- 25
- 30
Show the answer and the worked solution
Correct answer: C. 25
Worked solution
- Total work = 15 × 20 = 300 man-days.
- Men needed = 300 ÷ 12 = 25.
Answer: 25.
The idea
Inverse variation keeps the product fixed; direct variation keeps the ratio fixed. Deciding which applies is the only real step.
Shortcut. The days shrink by 12/20 = 3/5, so the men must grow by 5/3: 15 × 5/3 = 25.
Common trap. "30" — treating 12 days as roughly half of 20 and doubling the men; 30 men would finish in 300 ÷ 30 = 10 days.