CalcElfCalcElf › Shared work: 4 days and 12 days alone
Shared work: 4 days and 12 days alone
One worker alone can finish a job in 4 days, and another alone can finish the same job in 12 days. Working together, how many days do they need?
Answer
3 days
Step-by-step
- 1 ÷ 4 = 0.25Work done per day by A
- 1 ÷ 12 = 0.0833Work done per day by B
- 1 ÷ (0.25 + 0.0833) = 3Combined 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 4 and 12 days.
- Adding the two times and using that sum as the answer.