document.write( "Question 223231: I need a real-world example when the solution of a system of linear equations must be in the first quadrant. What do I need to know? \n" ); document.write( "
Algebra.Com's Answer #166955 by drj(1380)\"\" \"About 
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I need a real-world example when the solution of a system of linear equations must be in the first quadrant. What do I need to know?\r
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\n" ); document.write( "\n" ); document.write( "Here's an example:\r
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\n" ); document.write( "\n" ); document.write( "Donnie has $5.10 in nickels, dimes, and quarters. He has an equal number of dimes and nickels, with the value of the quarters being $2.40 more than the total value of the dimes and nickels. How many dimes does he have?\r
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\n" ); document.write( "\n" ); document.write( "Step 1. Let x be the number of nickels\r
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\n" ); document.write( "\n" ); document.write( "Step 2. Let x be the number of dimes since they are equal in number with the nickels.\r
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\n" ); document.write( "\n" ); document.write( "Step 3. Let \"%280.05%2B0.10%29x=0.15x\" be the dollar values of nickels and dimes.\r
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\n" ); document.write( "\n" ); document.write( "Step 4. Let 0.25y be the dollar values of quarters.\r
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\n" ); document.write( "\n" ); document.write( "Step 5. \"2.40%2B0.15x=0.25y\" since the value of the quarters being $2.40 more than the total value of the dimes and nickels. Or rewriting it as\r
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\n" ); document.write( "\n" ); document.write( "\"-0.15x%2B0.25y=2.40\"\r
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\n" ); document.write( "\n" ); document.write( "Step 6. Also, \"0.15x%2B0.25y=5.10\" as given by the problem since $5.10 in nickels, dimes, and quarters.\r
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\n" ); document.write( "\n" ); document.write( "Step 7. Now, we have a linear system of equations in Steps 5 and 6\r
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\n" ); document.write( "\n" ); document.write( "\"-0.15x%2B0.25y=2.40\" Equation A
\n" ); document.write( "\"0.15x%2B0.25y=5.10\" Equation B\r
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\n" ); document.write( "\n" ); document.write( "Adding Equations A and B\r
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\n" ); document.write( "\n" ); document.write( "\"-0.15x%2B0.15x%2B0.25y%2B0.25y=2.40%2B5.10\"\r
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\n" ); document.write( "\n" ); document.write( "\"0.50y=7.50\"\r
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\n" ); document.write( "\n" ); document.write( "\"y=15\" quarters\r
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\n" ); document.write( "\n" ); document.write( "Then solving x from Equation B is \"5.10-3.75=0.15x\" or \"x=9\".\r
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\n" ); document.write( "\n" ); document.write( "Check Equation A if true \"-0.15x%2B0.25y=2.40\" or \"-1.35%2B3.75=2.40\"...which is a true statement.\r
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\n" ); document.write( "\n" ); document.write( "Step 8. ANSWER: The number of nickels and dimes is 9 each and the number of quarters is 15.\r
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\n" ); document.write( "\n" ); document.write( "I hope the above steps were helpful.\r
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\n" ); document.write( "\n" ); document.write( "For FREE Step-By-Step videos in Introduction to Algebra, please visit http://www.FreedomUniversity.TV/courses/IntroAlgebra and for Trigonometry visit http://www.FreedomUniversity.TV/courses/Trigonometry.\r
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\n" ); document.write( "\n" ); document.write( "Good luck in your studies!\r
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\n" ); document.write( "\n" ); document.write( "Respectfully,
\n" ); document.write( "Dr J\r
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