<PRE><B>Question 184018</B>
Lourdes can trim the hedges around her property in 8 hours by using an electric hedge trimmer. Rafael can do the same job in 15 hours by using a manual trimmer. How long would it take them to trim the hedges working together? 
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Lourdes DATA:
time = 8 hr/job ; rate = 1/8 job/hr.
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Rafael DATA:
time = 15 hr/job ; rate = 1/15 job/hr.
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Together DATA:
time = x hr/job ; rate = 1/x job/hr
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Equation:
rate + rate = together rate
1/8 + 1/15 = 1/x

Multiply thru by 120x to get:
15x + 8x= 120
23x = 120
x = 5.21 hrs (time to trim the hedges together)
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Cheers,
Stan H.
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