A is twice as efficient as B — Time & Work Aptitude Question
A is twice as efficient as B: A is twice as efficient as B, and together they finish a job in 8 days. Answer and worked solution on CodeKairo.
- Topic: Time & Work
- Section: Quantitative Aptitude
- Difficulty: Medium
- Time target: 50 seconds
Question
A is twice as efficient as B, and together they finish a job in 8 days. How long would B alone take?
Options
- 12 days
- 16 days
- 24 days
- 32 days
Show the answer and the worked solution
Correct answer: C. 24 days
Worked solution
- Let B's rate be 1 unit/day; A's is 2 units/day; together 3 units/day.
- Total work = 3 × 8 = 24 units.
- B alone: 24/1 = 24 days.
Answer: 24 days.
The idea
Efficiency ratios translate directly into rate ratios. Pick the smallest rate as 1 unit and everything else follows.
Shortcut. B supplies one-third of the combined rate, so alone he takes 3 × 8 = 24 days (A, with two-thirds, takes 1.5 × 8 = 12).
Common trap. 12 days — A's time, not B's; B is the slower worker, so his time must be the longer one.