document.write( "Question 158245: I got the question incorrect, but I do not know what I did wrong.\r
\n" ); document.write( "\n" ); document.write( "The cost of manufacturing notebooks varies inversely as the number of notebooks. If it costs 50 cents a notebook when 10,000 are manufactured, how much will it cost if 18,000 are made?\r
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\n" ); document.write( "50/10,000=x/18,000\r
\n" ); document.write( "\n" ); document.write( "1/200=x/18,000 \r
\n" ); document.write( "\n" ); document.write( "200x=18,000
\n" ); document.write( "x=90 cents \n" ); document.write( "

Algebra.Com's Answer #116621 by Edwin McCravy(20059) $\"\"$ $\"About$

You can put this solution on YOUR website!
I got the question incorrect, but I do not know what I did wrong.\r
\n" ); document.write( "\n" ); document.write( "The cost of manufacturing notebooks varies inversely as the number of notebooks. If it costs 50 cents a notebook when 10,000 are manufactured, how much will it cost if 18,000 are made?\r
\n" ); document.write( "\n" ); document.write( "MY WORK:
\n" ); document.write( " $\"50%2F10%2C000=x%2F18000\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"1%2F200=x%2F18000\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"200x=18000\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"x=90\"$ cents\r
\n" ); document.write( "\n" ); document.write( "

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document.write( "That method is OK for direct variation, but not\r\n" );
document.write( "for inverse variation.  \r\n" );
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document.write( "Indirect variation is the \"cheaper by the dozen\" idea.\r\n" );
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document.write( "In direct variation, when one quantity goes up, the other goes up \r\n" );
document.write( "also, and when one goes down, the other goes down also.\r\n" );
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document.write( "But in indirect variation, when one quantity goes up, the other\r\n" );
document.write( "goes down, and vice-versa.\r\n" );
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document.write( "So in this problem, when the production goes up from 10,000 to\r\n" );
document.write( "18,000, you should expect the cost per notebook to go down.  So\r\n" );
document.write( "you should expect an answer less than 50 cents, not more!\r\n" );
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document.write( "Here is how to handle this inverse proportion problem:\r\n" );
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document.write( "Start this:\r\n" );
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document.write( "Substitute  and \r\n" );
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document.write( "Multiply both sides by \r\n" );
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document.write( "Substitute this into \r\n" );
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document.write( "Now substitute \r\n" );
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document.write( "cents\r\n" );
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document.write( "or about 27.78 cents cost per notebook.\r\n" );
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document.write( "Edwin

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