document.write( "Question 1043245: A and B can build a wall in 15 and 20 hrs resp.
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\n" ); document.write( "they worked together they use 180 bricks less
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Algebra.Com's Answer #658363 by Edwin McCravy(20054)\"\" \"About 
You can put this solution on YOUR website!
A and B can build a wall in 15 and 20 hrs resp.
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document.write( "Suppose there are N bricks in the wall.\r\n" );
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document.write( "A can lay N bricks in 15 hours, so A's brick-laying rate is \r\n" );
document.write( "N bricks per 15 hours or N/15 bricks per hour.\r\n" );
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document.write( "B can lay N bricks in 20 hours, so B's brick-laying rate is \r\n" );
document.write( "N bricks per 20 hours or N/20 bricks per hour.\r\n" );
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\n" ); document.write( "if they worked together they use 180 bricks less
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document.write( "Whoa!  180 bricks less per hour than what? 180 bricks less per\r\n" );
document.write( "hour than A's rate in bricks per hour? -- or 180 bricks less per hour\r\n" );
document.write( "than B's rate in bricks per hour?  We can't continue until we know \r\n" );
document.write( "what to subtract 180 from.  And you didn't tell us.  \r\n" );
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document.write( "I'll try to go on anyway without that and see what happens:\r\n" );
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document.write( "Their combined brick-laying rate is (N/15 + N/20) bricks per\r\n" );
document.write( "hour.   Getting an LCD of 60, their combined brick-laying rate works \r\n" );
document.write( "out to be (7N/60) bricks per hour. \r\n" );
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\n" ); document.write( "and build the wall in 12 hrs .
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document.write( "That says their combined brick-laying rate is N bricks laid in\r\n" );
document.write( "12 hours or N/12 bricks per hour.\r\n" );
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document.write( "So we set those equal:\r\n" );
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document.write( "7N/60 = N/12\r\n" );
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document.write( "Cross multiplying\r\n" );
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document.write( "84N = 60N\r\n" );
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document.write( "Dividing both sides by N\r\n" );
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document.write( "84 = 60\r\n" );
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document.write( "Sorry. This problem is botched.  Look at the problem again,\r\n" );
document.write( "and carefully type it out word-for-word (don't abbreviate and \r\n" );
document.write( "don't leave anything out) in the thank-you note form below and \r\n" );
document.write( "I'll get back to you by email.\r\n" );
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document.write( "Edwin
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