document.write( "Question 308994: Dave can dig a ditch in 6 hours, and Sam can dig a ditch in 4 hours. Frank can fill a ditch in 8 hours. If Dave and Sam dig a ditch while Frank tries to fill it, how long does it take to dig the ditch altogether? \n" ); document.write( "
Algebra.Com's Answer #220954 by mananth(16946)\"\" \"About 
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Dave can dig aditch in6 hours
\n" ); document.write( "So he can do 1/6 of job in 1 hour
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\n" ); document.write( "Sam can dig in 4 hours.
\n" ); document.write( "so he can do 1/4 of the job in 1 hour
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\n" ); document.write( "Frank fills the ditch in 8 hours
\n" ); document.write( "So he can do 1/8 of the job of filling in 1 hour
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\n" ); document.write( "1/6 + 1/4 of the job of digging they do in 1 hour
\n" ); document.write( "=2+3 /12
\n" ); document.write( "= 5/12\r
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\n" ); document.write( "5/12 - 1/8 is the effective digging in 1 hour
\n" ); document.write( "10-3 / 24
\n" ); document.write( "=7/24 is the effective digging in 1 hour
\n" ); document.write( "So to complete the job of digging they will take 24/7 hours
\n" ); document.write( "= 3.42 hours \r
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