Question 1206703
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Let's say the job is to move 80 boxes.


Billy can do the job in 8 hours when working alone. 
His unit rate is 80/8 = 10 boxes per hour.
rate = amountDone/time


When Allen works alone, his rate is 5 times faster, so it is 5*10 = 50 boxes per hour.


Combined rate = 10+50 = 60 boxes per hour assuming neither person slows down the other.


rate*time = amountDone
time = amountDone/rate
time = 80/60 of an hour
time = 4/3 of an hour
time = 1 & 1/3 of an hour
time = 1 hour + 20 minutes
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