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| Math Central | Quandaries & Queries |
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Question from Rajesh, a student: Worker A can do a piece of work in 15 days, worker B in 12 days, and worker C in 10 days. Worker A works 2 days, worker B 3 days, and worker C 3 days. In what time can worker A and worker B finish the job by working together? |
Hi Rajesh,
You need to look at the rates at which the three employees work.
A can do the job in 15 days so he works at 1/15 of a job per day.
B can do the job in 12 days so he works at 1/12 of a job per day.
C can do the job in 10 days so he works at 1/10 of a job per day.
Worker A works 2 days, worker B 3 days, and worker C 3 days so the proportion of the job completed is
2/15 + 3/12 + 3/10 .
How much of the job remains?
A and B working together work at the rate of (1/15 + 1/12) of a job per day. How long will it take them to complete the remaining part of the job?
Penny
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