Constant Work-Rates Rule, R*T=J
R is rate in JOBS/TIME;
T is Time;
J is how many jobs.
Combined work rate for two agents working on the same job is the SUM of the individual rates.
Tabulating the given information can often help.
RATE TIME JOB Quantity
Laura 1/5 5 1
Bill r
Combined 1/3 3 1
This helps to find Bill's rate.
-------Bill's rate in jobs per hour.
Now you want to calculate HOW MUCH of the job did each Bill and Laura do, when they worked together for that three hours.
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Bill:
Laura:
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You can try to check this. The sum of those two PARTS of the 1 job should be 1.
, so this seems sensible.
You can change these to percents if you want.