document.write( "Question 869045: A boy has only dimes and quarters in his piggy bank. If he has 60 coins worth 12 dollars and 45 cents altogether, how many quarters does he have in his bank?
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Algebra.Com's Answer #524196 by LinnW(1048)\"\" \"About 
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Set q = number of quarters
\n" ); document.write( "d = number of dimes
\n" ); document.write( "($0.25 * q ) + ($0.10 * d ) = $12.45
\n" ); document.write( "0.25q + 0.10d = 12.45
\n" ); document.write( "multiply each side by 100
\n" ); document.write( "25q + 10d = 1245
\n" ); document.write( "We also know that q + d = 60
\n" ); document.write( "If we add -d to each side
\n" ); document.write( "q + d - d = 60 - d
\n" ); document.write( "q = 60 - d
\n" ); document.write( "Substitute (60 - d) for q in 25q + 10d = 1245
\n" ); document.write( "25(60 - d) + 10d = 1245
\n" ); document.write( "1500 - 25d + 10d = 1245
\n" ); document.write( "1500 -15d = 1245
\n" ); document.write( "add -1500 to each side
\n" ); document.write( " -15d = -255
\n" ); document.write( "divide each side by -15
\n" ); document.write( " d = -255/-15
\n" ); document.write( " d = 17
\n" ); document.write( "Since q + d = 60
\n" ); document.write( " q + 17 = 60
\n" ); document.write( "add -17 to each side
\n" ); document.write( " q = 43
\n" ); document.write( "43 quarters is $10.75
\n" ); document.write( "17 dimes is $1.70
\n" ); document.write( "$10.75 + $1.70 = $12.45 so we have a good solution \n" ); document.write( "
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