CalcElfCalcElf › Shared work: 10 days and 15 days alone
Shared work: 10 days and 15 days alone
One worker alone can finish a job in 10 days, and another alone can finish the same job in 15 days. Working together, how many days do they need?
Answer
6 days
Step-by-step
- 1 ÷ 10 = 0.1Work done per day by A
- 1 ÷ 15 = 0.0667Work done per day by B
- 1 ÷ (0.1 + 0.0667) = 6Combined time = 1 ÷ combined rate
Why it works
Working together, the two work rates add: each rate is 1 divided by that person's own time, so the shared time is 1 divided by the sum of the two rates.
Common mistakes
- Taking the average of 10 and 15 days.
- Adding the two times and using that as the answer.