document.write( "Question 1200356: Jane has a pre-paid cell phone with Splint. She can't remember the exact costs, but her plan has a monthly fee and a charge for each minute of calling time. In June she used 130 minutes and the cost was $76.50. In July she used 510 minutes and the cost was $209.50.\r
\n" ); document.write( "\n" ); document.write( "A) Express the monthly cost as C as a function of X, the number of minutes of calling time she used.
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\n" ); document.write( "\n" ); document.write( "B) If Jane used 205 minutes of calling time in August, how much was her bill?
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Algebra.Com's Answer #834481 by ikleyn(52787) $\"\"$ $\"About$

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\n" ); document.write( "Jane has a pre-paid cell phone with Splint. She can't remember the exact costs, but her plan has a monthly fee
\n" ); document.write( "and a charge for each minute of calling time.
\n" ); document.write( "In June she used 130 minutes and the cost was $76.50.
\n" ); document.write( "In July she used 510 minutes and the cost was $209.50.
\n" ); document.write( "A) Express the monthly cost as C as a function of X, the number of minutes of calling time she used.\r
\n" ); document.write( "\n" ); document.write( "B) If Jane used 205 minutes of calling time in August, how much was her bill?
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document.write( "The difference in the cost, 209.50 - 76.50 = 133 dollars, is due to the difference of minutes\r\n" );
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document.write( "    510 - 130 = 380 minutes.\r\n" );
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document.write( "Hence, each minute costs   = 0.35 dollars.\r\n" );
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document.write( "Now we can compute the monthly fee.  It is  76.50 - 130*0.35 = 31.00  dollars,\r\n" );
document.write( "from the June's bill.\r\n" );
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document.write( "Hence, the cost function is  C(X) = 31 + 0.35*X.\r\n" );
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document.write( "It is your ANSWER to question (A).\r\n" );
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document.write( "To answer question (B), you should calculate\r\n" );
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document.write( "    C(205) = 31 + 0.35*205 = 102.75 dollars.\r\n" );
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document.write( "It is the ANSWER  to question (B).\r\n" );
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\n" ); document.write( "\n" ); document.write( "Solved.\r
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