SOLUTION: A mason can lay the bricks in a sidewalk in 10 hours. The mason's apprentice requires 12 hours to do the same job. After working together for 3 hours, the mason leaves for another

Question 1125451: A mason can lay the bricks in a sidewalk in 10 hours. The mason's apprentice requires 12 hours to do the same job. After working together for 3 hours, the mason leaves for another job and the apprentice continues working. How long will it take the apprentice to complete the job? (Round your answer to two decimal places.)

Answer by rothauserc(4718) (Show Source): You can put this solution on YOUR website!
the hourly rate for the mason is 1/10
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the mason's apprentice's hourly rate is 1/12
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together 1/10 + 1/12 = 11/60 per hour is their combined rate
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taking the reciprocal, 60/11 hours to complete the job together
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together they worked at a rate of 11/60 for three hours
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11/60 * 3 = 11/20 of the job was done in 3 hours
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this leaves 1 - 11/20 = 9/20 of the job for the apprentice
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divide by the apprentice's rate (9/20)/(1/12) = 9/20 * 12/1 = 9/5 * 3 = 27/5
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it takes the apprentice 5.40 hours to complete the job
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