document.write( "Question 1200128: A small grain combine can harvest 100 acres in 24 hours, a medium combine can do the same job in 18 hours, and a large combine can do the job in 12 hours. If all three combines are used at the same time, how long will it take to harvest 800 acres? \n" ); document.write( "

Algebra.Com's Answer #834155 by josgarithmetic(39617) $\"\"$ $\"About$

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First task could be, find the rate of all three machines working together.
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document.write( "WHICH MACHINE          RATE, acres per hours\r\n" );
document.write( "small                   100/24\r\n" );
document.write( "medium                  100/18\r\n" );
document.write( "large                   100/12\r\n" );
document.write( "All-Together       100/24+100/18+100/12\r\n" );
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\n" ); document.write( "\n" ); document.write( " $\"%283%2F3%29%28100%2F24%29+%2B+%284%2F4%29%28100%2F18%29+%2B+%286%2F6%29%28100%2F12%29\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"300%2F72%2B400%2F72%2B600%2F72\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"1300%2F72\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"325%2F18\"$ --------the rate of three-combined machines\r
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\n" ); document.write( "\n" ); document.write( "800 acres, how much time?\r
\n" ); document.write( "\n" ); document.write( " $\"%28325%2F18%29%2Ax=800\"$ \r
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\n" ); document.write( "\n" ); document.write( " $\"x=800%2818%2F325%29\"$ \r
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\n" ); document.write( "\n" ); document.write( "44 hours 19 minutes \n" ); document.write( "

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