document.write( "Question 336947: A window washer can wash the windows on one side of a building in 72 working hours. With an assistant he can do the job in 40 hours. How many hours would the assistant take to do the job working alone? \n" ); document.write( "

Algebra.Com's Answer #241499 by stanbon(75887) $\"\"$ $\"About$

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A window washer can wash the windows on one side of a building in 72 working hours.
\n" ); document.write( "W W DATA:
\n" ); document.write( "time = 72 hrs/job
\n" ); document.write( "rate = 1/72 job/hr
\n" ); document.write( "----------------------------
\n" ); document.write( " With an assistant he can do the job in 40 hours.
\n" ); document.write( "Together DATA:
\n" ); document.write( "time = 40 hrs/job
\n" ); document.write( "rate = 1/40 job/hr
\n" ); document.write( "----------------------
\n" ); document.write( "Assistant DATA:
\n" ); document.write( "time = x hrs/job
\n" ); document.write( "rate = 1/x job/hr
\n" ); document.write( "-----------------------
\n" ); document.write( "How many hours would the assistant take to do the job working alone?
\n" ); document.write( "Equation:
\n" ); document.write( "rate + rate = together rate
\n" ); document.write( "1/72 + 1/x = 1/40
\n" ); document.write( "----
\n" ); document.write( "Multiply thru by 40*72x to get:
\n" ); document.write( "40x + 40*72 = 72x
\n" ); document.write( "32x = 40*72
\n" ); document.write( "x = 90 hrs (time the assistant would need to do the job alone)
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\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H.
\n" ); document.write( "========== \n" ); document.write( "

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