document.write( "Question 1104645: If two people work at washing 5 cars and one can do all 5 cars on their own in 36 minutes and the other can do all 5 on their own in 42 minutes, how long does it take to wash all 5 working together? \n" ); document.write( "
Algebra.Com's Answer #719429 by ankor@dixie-net.com(22740)\"\" \"About 
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If two people work at washing 5 cars and one can do all 5 cars on their own in 36 minutes and the other can do all 5 on their own in 42 minutes, how long does it take to wash all 5 working together
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\n" ); document.write( "let t = time required working together
\n" ); document.write( "let the completed job = 1 (the washing of 5 cars)
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\n" ); document.write( "Each will do a fraction of the job; the two fractions add up to 1
\n" ); document.write( "\"t%2F36\" + \"t%2F42\" = 1
\n" ); document.write( "multiply by the least common multiplier;252, cancel the denominators
\n" ); document.write( "252*\"t%2F36\" + 252*\"t%2F42\" = 252
\n" ); document.write( "7t + 6t = 252
\n" ); document.write( "13t = 252
\n" ); document.write( "t = 252/13
\n" ); document.write( "t = 19.4 min working together
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\n" ); document.write( "Check
\n" ); document.write( "\"19.4%2F36\" + \"19.4%2F42\" =
\n" ); document.write( ".539 + .462 = 1.00\r
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