Twice as fast — Time & Work Aptitude Question
Twice as fast: A works twice as fast as B. Together they finish a job in 12 days. How long would B alone take? Answer and worked solution on CodeKairo.
- Topic: Time & Work
- Section: Quantitative Aptitude
- Difficulty: Medium
- Time target: 60 seconds
Question
A works twice as fast as B. Together they finish a job in 12 days. How long would B alone take?
Options
- 18 days
- 24 days
- 30 days
- 36 days
Show the answer and the worked solution
Correct answer: D. 36 days
Worked solution
- Let B's rate be 1 unit/day; then A's is 2, and together 3 units/day.
- Total work = 3 × 12 = 36 units.
- B alone: 36 ÷ 1 = 36 days.
Answer: 36 days.
The idea
Efficiency ratios become rate ratios directly. Set the slowest rate to 1 unit and everything else follows without fractions.
Shortcut. B supplies 1 of the pair's 3 shares of output, so alone B needs 3 × 12 = 36 days (and A needs 1.5 × 12 = 18).
Common trap. 18 days — A's time alone; A is the faster worker, while the question asks about B.