Question 260741: Working alone, Andy can rake the leaves in his yard in 3 hours. His sister Emma, working alone,can rake the leaves in 4 and a half hours. If they work together,to the nearest minute, how quickly can they rake the leaves?
Answer by Alan3354(69443)   (Show Source):
You can put this solution on YOUR website! Working alone, Andy can rake the leaves in his yard in 3 hours. His sister Emma, working alone,can rake the leaves in 4 and a half hours. If they work together,to the nearest minute, how quickly can they rake the leaves?
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The hard way:
Andy does 1/3 of the yard per hour.
Emma does 1/4 of the yard per hour.
Together, they do 1/3 + 1/4 = 7/12 per hour.
--> 12/7 hours to do the yard.
= 720/7 minutes = 103 minutes.
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The easy way, product/sum
3*4/(3+4) = 12/7 hours
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