document.write( "Question 426466: Riva takes 5 hours to do a job. If Megan takes 8 hours and Sarah takes 10 hours to do the same job, then how many hours will it take all of them to do the job if they work together? \n" ); document.write( "
Algebra.Com's Answer #296706 by J2R2R(94)\"\" \"About 
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Time
\n" ); document.write( "Riva = 5 hours
\n" ); document.write( "Megan = 8 hours
\n" ); document.write( "Sarah = 10 hours\r
\n" ); document.write( "\n" ); document.write( "Speed
\n" ); document.write( "Riva = 1/5 of the job per hour
\n" ); document.write( "Megan = 1/8 of the job per hour
\n" ); document.write( "Sarah = 1/10 of the job per hour\r
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\n" ); document.write( "\n" ); document.write( "Combine all speeds
\n" ); document.write( "All = 1/5 + 1/8 + 1/10 = 8/40 + 5/40 + 4/40 = 17/40 of the job per hour\r
\n" ); document.write( "\n" ); document.write( "Therefore for the complete job to be done it will take 40/17 hours.\r
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\n" ); document.write( "\n" ); document.write( "This may seem complex but let us give an example.
\n" ); document.write( "Let us say the job comprised of 40 units
\n" ); document.write( "Riva would do 8 units an hour for 5 hours
\n" ); document.write( "Megan would do 5 units an hour for 8 hours
\n" ); document.write( "Sarah would do 4 units and hour for 10 hours
\n" ); document.write( "Their combined effort per hour is 17 units
\n" ); document.write( "To do 40 units will therefore take 40/17 hours.
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