Twenty-five percent more efficient — Aptitude Question
Twenty-five percent more efficient: A is 25% more efficient than B and takes 10 days less to finish a job. Answer and worked solution on CodeKairo.
- Topic: Time & Work
- Section: Quantitative Aptitude
- Difficulty: Hard
- Time target: 105 seconds
Question
A is 25% more efficient than B and takes 10 days less to finish a job. How many days does A take?
Options
- 30
- 40
- 45
- 50
Show the answer and the worked solution
Correct answer: B. 40
Worked solution
- A's time = B's time ÷ 1.25 = 0.8 × B's time.
- t − 0.8t = 10 → 0.2t = 10 → t = 50.
- B takes 50 days, so A takes 0.8 × 50 = 40 days.
Answer: 40 days.
The idea
Efficiency and time are inversely proportional: 25% more efficient means 20% less time. Converting the percentage correctly is the crux.
Shortcut. Efficiency 5 : 4 means time 4 : 5, so the 10-day gap is one part and A takes 4 × 10 = 40 days.
Common trap. 50 — B's time, the first number the equation 0.2t = 10 produces; A takes 0.8 × 50.