Four-fifths done in twenty days — Aptitude Question
Four-fifths done in twenty days: A completes four-fifths of a work in 20 days. How many more days will he take to… Answer and worked solution on CodeKairo.
- Topic: Time & Work
- Section: Quantitative Aptitude
- Difficulty: Easy
- Time target: 45 seconds
Question
A completes four-fifths of a work in 20 days. How many more days will he take to finish the rest?
Options
- 4 days
- 5 days
- 6 days
- 8 days
Show the answer and the worked solution
Correct answer: B. 5 days
Worked solution
- 4/5 of the work took 20 days, so 1/5 takes 20 ÷ 4 = 5 days.
- (The whole job would take 25 days.)
Answer: 5 days.
The idea
Scale the fraction directly rather than computing the full-job time first. Both work, but the direct route is one division.
Shortcut. Work left : work done = 1 : 4, so the time left is 20 ÷ 4 = 5 days; the whole job is 25 days, which checks.
Common trap. 4 days — dividing 20 by 5 (the denominator) instead of by 4, the number of fifths already done.