document.write( "Question 480874: Angela takes 40 minutes to dust and clean her home while her sister rani takes an hour (6o min) to do same work. One day their mother joins the two sisters and together the three of them dust and clean their house in just 15 min. How long would their mother take if she did the job alone. \n" ); document.write( "

Algebra.Com's Answer #329275 by nerdybill(7384) $\"\"$ $\"About$

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Angela takes 40 minutes to dust and clean her home while her sister rani takes an hour (6o min) to do same work. One day their mother joins the two sisters and together the three of them dust and clean their house in just 15 min. How long would their mother take if she did the job alone.
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\n" ); document.write( "Let x = time (min) for mother to do it alone
\n" ); document.write( "then
\n" ); document.write( "15(1/40 + 1/60 + 1/x) = 1
\n" ); document.write( "multiplying both sides by 2400x:
\n" ); document.write( "15(60x + 40x + 2400) = 2400x
\n" ); document.write( "15(100x + 2400) = 2400x
\n" ); document.write( "1500x + 36000 = 2400x
\n" ); document.write( "36000 = 900x
\n" ); document.write( "40 mins = x\r
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