Time and Work aptitude questions
Time and Work questions are part of the Quant section of placement aptitude tests. Turn each worker into a per-day rate and add rates, not days. Below are 5 worked examples with the answer and the working; practise ten fresh ones or take a timed mock when you are ready.
Example 1. A can do a job in 4 days and B in 12 days. If they work together, how many days will they need to finish half the job?
- A. 2.5 days
- B. 1.5 days (answer)
- C. 16 days
- D. 0.5 days
Together they finish 1/4 + 1/12 = 0.3 of the job per day. Half the job needs 0.5/0.3 = 1.5 days.
Example 2. A can finish a job in 12 days and B can finish it in 24 days. Working together, in how many days will they finish it?
- A. 24 days
- B. 36 days
- C. 18 days
- D. 8 days (answer)
In one day they finish 1/12 + 1/24 of the job. Together the time is ab/(a + b) = 12 * 24/(12 + 24) = 8 days.
Example 3. A alone can finish a job in 9 days. A and B together finish it in 6 days. In how many days can B alone finish it?
- A. 6 days
- B. 18 days (answer)
- C. 27 days
- D. 9 days
B's one day work is 1/6 - 1/9 = 1/18, so B alone needs 18 days.
Example 4. A alone can finish a job in 10 days. A and B together finish it in 6 days. In how many days can B alone finish it?
- A. 15 days (answer)
- B. 10 days
- C. 6 days
- D. 25 days
B's one day work is 1/6 - 1/10 = 1/15, so B alone needs 15 days.
Example 5. A alone can finish a job in 5 days. A and B together finish it in 4 days. In how many days can B alone finish it?
- A. 20 days (answer)
- B. 25 days
- C. 5 days
- D. 4 days
B's one day work is 1/4 - 1/5 = 1/20, so B alone needs 20 days.
More Quant practice elsewhere: IndiaBIX, GeeksforGeeks. See the 60-day aptitude plan.