document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=449356>Question 449356</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The monthly cost (in dollars) of a long-distance phone plan is a linear function of the total calling time (in minutes). The monthly cost for 34 minutes of calls is $12.47 and the monthly cost for 51 minutes is $14.00. What is the monthly cost for 47 minutes of calls?  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #309171 by </B><A HREF=/tutors/aboutme.mpl?userid=lwsshak3><B>lwsshak3(11628)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=lwsshak3><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=309171\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The monthly cost (in dollars) of a long-distance phone plan is a linear function of the total calling time (in minutes). The monthly cost for 34 minutes of calls is $12.47 and the monthly cost for 51 minutes is $14.00. What is the monthly cost for 47 minutes of calls.<BR>\n" );
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document.write( "The standard form for a linear or straight-line function is: y=mx+b, where m=slope, and b, the y-intercept. Since you have two points of the function, you are able to find the slope m= &#8710;y/&#8710;x.<BR>\n" );
document.write( "For given problem:<BR>\n" );
document.write( "m=(14.00-12.47)/(51-34)=1.53/17<BR>\n" );
document.write( "The equation can now be written: y=(1.53/17)x+b<BR>\n" );
document.write( "To complete the equation we need to find b.<BR>\n" );
document.write( "Plug in the (x,y) values from one of the given points and solve for b<BR>\n" );
document.write( "14=51(1.53/17)+b<BR>\n" );
document.write( "b=14-51(1.53/17)=9.41<BR>\n" );
document.write( "You now have an equation to calculate the monthly cost for any number of calling minutes:<BR>\n" );
document.write( "y=1.53x/17+9.41<BR>\n" );
document.write( "For 47 minutes of calls,<BR>\n" );
document.write( "y=1.53*47/17+9.41=13.64\r<BR>\n" );
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document.write( "ans:<BR>\n" );
document.write( "For 47 minutes of calling the monthly cost is $13.64\r<BR>\n" );
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document.write( "see the graph of this straight-line function below\r<BR>\n" );
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document.write( "..\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=+graph%28+300%2C+300%2C+-5%2C+60%2C+-5%2C+20%2C+1.53x%2F17%2B9.41%29+ ALIGN=MIDDLE  ALT=\"+graph%28+300%2C+300%2C+-5%2C+60%2C+-5%2C+20%2C+1.53x%2F17%2B9.41%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" > </SPAN>\n" );
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