Question

Suppose that a person with a push mower can mow a large lawn in 5 ​hours, whereas the lawn can be mowed with a riding lawn mower in 3 hours. working​ together, how long will it take to mow the​ lawn?

Answer 1

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Push Mower
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It takes 5 hours to complete the job
1 hour = 1/5 of the job

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Riding Lawn Mower
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It takes 3 hours to complete the job
1 hour = 1/3 of the job

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Push Mower + Riding Lawn Mower
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1 hour = 1/5 + 1/3 
1 hour = 3/15 + 5/15 
1 hour = 8/15 of the job.

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Calculate time needed to complete
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8/15 of the job takes 1 hour
8/15 of the job = 1 hour 

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Divide by 8/15 on both side
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8/15 ÷ 8/15 of the job = 1 ÷ 8/15 hour
Whole of the job = 1 x 15/8 hours
Whole of the job = 15/8 hours
Whole of the job = 1 7/8 hours

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Answer: 1 7/8 hours
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