document.write( "Question 214871: I've figured out the answer but don't know the formula to arrive at it. The problem is: Warren has 40 coins (all nickels, dimes and quarters) worth $4.05. He has 7 more nickles than dimes. How many quarters does Warren have?\r
\n" ); document.write( "\n" ); document.write( "The answer is 13 dimes, 20 nickles and 7 quarters, I figured from trial and error relatively easily, but I can't come up with the equation. Can you help? Thanks, \n" ); document.write( "
Algebra.Com's Answer #162339 by Alan3354(69443)\"\" \"About 
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I've figured out the answer but don't know the formula to arrive at it. The problem is: Warren has 40 coins (all nickels, dimes and quarters) worth $4.05. He has 7 more nickles than dimes. How many quarters does Warren have?
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\n" ); document.write( "n + d + q = 40 (total of coins)
\n" ); document.write( "n = d + 7 (7 more nickels than dimes)
\n" ); document.write( "5n + 10d + 25q = 405 (value of coins)
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\n" ); document.write( "Sub for n = 1st and 3rd eqns
\n" ); document.write( "(d+7) + d + q = 40
\n" ); document.write( "5(d+7) + 10d + 25q = 405
\n" ); document.write( "----------------
\n" ); document.write( "2d + q = 33 --> 10d + 5q = 165
\n" ); document.write( "15d + 25q = 370 --> 3d + 5q = 74
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\n" ); document.write( "10d + 5q = 165
\n" ); document.write( "3d + 5q = 74
\n" ); document.write( "-------------- Subtract
\n" ); document.write( "7d = 91
\n" ); document.write( "d = 13
\n" ); document.write( "-------
\n" ); document.write( "Sub for d, find q
\n" ); document.write( "q = 7
\n" ); document.write( "-------
\n" ); document.write( "n = 20\r
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