document.write( "Question 615961: please help
\n" ); document.write( "The cost of six CDs and four DVDs is $77.80; and the cost of fourteen DVDs and eleven CDs is $192.25. How much do a CD and a DVD cost? \n" ); document.write( "

Algebra.Com's Answer #387408 by JBarnum(2146) $\"\"$ $\"About$

You can put this solution on YOUR website!
c=cds d=dvds
\n" ); document.write( " $\"6c%2B4d=77.8\"$
\n" ); document.write( " $\"11c%2B14d=192.25\"$
\n" ); document.write( "personally i think elimination method with eliminating the dvds would be the easiest. 14 gos into 28 2 times and 4 goes into 28 7 times
\n" ); document.write( "so multiply the top equation by 7 and bottom equation bt 2
\n" ); document.write( " $\"7%286c%2B4d%29=7%2877.8%29\"$
\n" ); document.write( " $\"2%2811c%2B14d%29=2%28192.25%29\"$
\n" ); document.write( ".
\n" ); document.write( " $\"7%286c%2B4d%29=7%2877.8%29\"$
\n" ); document.write( " $\"42c%2B28d=544.6\"$
\n" ); document.write( ".
\n" ); document.write( " $\"2%2811c%2B14d%29=2%28192.25%29\"$
\n" ); document.write( " $\"22c%2B28d=384.5\"$
\n" ); document.write( ".
\n" ); document.write( " $\"42c%2B28d=544.6%29\"$
\n" ); document.write( " $\"22c%2B28d=384.5%29\"$ now subtract the 2 equations
\n" ); document.write( " $\"42c-22c=20c\"$
\n" ); document.write( " $\"28d-28d=0\"$
\n" ); document.write( " $\"544.6-384.5=160.1\"$
\n" ); document.write( " $\"20c%2B0=160.1\"$ divide by 20
\n" ); document.write( " $\"c=8.005\"$
\n" ); document.write( "if rounding up then its $8.01 per cd
\n" ); document.write( "now take that number and put it in for c in one of the original equations\r
\n" ); document.write( "\n" ); document.write( " $\"6c%2B4d=77.8\"$
\n" ); document.write( " $\"6%288.01%29%2B4d=77.8\"$
\n" ); document.write( " $\"48.06%2B4d=77.8\"$ subtract 48.06
\n" ); document.write( " $\"4d=29.74\"$
\n" ); document.write( " $\"d=7.435\"$
\n" ); document.write( "if rounded up it would be $7.44 per dvd\r
\n" ); document.write( "\n" ); document.write( "check with second equation
\n" ); document.write( " $\"11c%2B14d=192.25\"$
\n" ); document.write( " $\"11%288.01%29%2B14%287.44%29=192.25\"$
\n" ); document.write( " $\"88.11%2B104.16=192.27\"$ hmm guess i shouldnt of rounded up
\n" ); document.write( ".
\n" ); document.write( " $\"6%288.005%29%2B4d=77.8\"$
\n" ); document.write( " $\"48.03%2B4d=77.8\"$ subtract 48.03
\n" ); document.write( " $\"4d=29.77\"$
\n" ); document.write( " $\"d=7.4425\"$
\n" ); document.write( ".
\n" ); document.write( " $\"11c%2B14d=192.25\"$
\n" ); document.write( " $\"11%288.005%29%2B14%287.4425%29=192.25\"$
\n" ); document.write( " $\"88.055%2B104.195=192.25\"$ ok that works
\n" ); document.write( "so dvds are $7.4425 each and cds are $8.005 each \n" ); document.write( "

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