Time and work

Work, efficiency, pipes and cisterns.

General Test6 questions
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Key ideas

  • If A finishes a job in a days, A’s one-day work is 1/a.
  • Working together: 1/a + 1/b of the job per day.
  • More workers, fewer days: workers × days stays constant for the same job.
  • Pipes and cisterns work the same way; emptying pipes count as negative work.

Practice questions

6 workers finish a job in 10 days. How many days will 12 workers take, working at the same rate?Easy
A can finish a job in 10 days and B in 15 days. Working together, they finish it in:Medium
8 workers build a wall in 12 days. How many days will 6 workers take?Easy
A pipe fills a tank in 4 hours and another empties it in 6 hours. With both open, the tank fills in:Medium
A does half as much work as B in the same time. If together they finish a job in 10 days, how long would B alone take?Hard

Practise all 6 questions as a set

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