document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=994439>Question 994439</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A phone company has a monthly cellular data plan where a customer pays a flat monthly fee of $10 and then a certain amount of money per megabyte (MB) of data used on the phone. If a customer uses 20 MB, the monthly cost will be $11.20. If the customer uses 130 MB, the monthly cost will be $17.80.<BR>\n" );
document.write( "A. Find a linear equation for the monthly cost of the data plan as a function of x, the number of MB used.<BR>\n" );
document.write( "B. Interpret the slope and vertical intercept of the equation.<BR>\n" );
document.write( "C. Use your equation to find the total monthly cost if 250 MB are used. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #613530 by </B><A HREF=/tutors/aboutme.mpl?userid=stanbon><B>stanbon(75887)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=stanbon><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=613530\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A phone company has a monthly cellular data plan where a customer pays a flat monthly fee of $10 and then a certain amount of money per megabyte (MB) of data used on the phone. If a customer uses 20 MB, the monthly cost will be $11.20. If the customer uses 130 MB, the monthly cost will be $17.80.<BR>\n" );
document.write( "A. Find a linear equation for the monthly cost of the data plan as a function of x, the number of MB used.<BR>\n" );
document.write( "-----<BR>\n" );
document.write( "You are given 2 points:: (20,10,21.20) ; (130,27.80)<BR>\n" );
document.write( "-----<BR>\n" );
document.write( "slope = (27.8-21.2)/(110) = 0.06<BR>\n" );
document.write( "-----<BR>\n" );
document.write( "Cost = 0.06x + b<BR>\n" );
document.write( "Solve for \"b\"<BR>\n" );
document.write( "21.20 = 0.06*20 + b<BR>\n" );
document.write( "21.2 = 1.2 + b<BR>\n" );
document.write( "b = 20<BR>\n" );
document.write( "Cost = 0.06x + 20<BR>\n" );
document.write( "-----------------<BR>\n" );
document.write( "----<BR>\n" );
document.write( "B. Interpret the slope and vertical intercept of the equation.<BR>\n" );
document.write( "slope = 0.60 means $0.06 or 6 cents extra for each MB over 20<BR>\n" );
document.write( "intercept = $20 for joining the plan and using less than 20 MB<BR>\n" );
document.write( "-------------------<BR>\n" );
document.write( "C. Use your equation to find the total monthly cost if 250 MB are used.<BR>\n" );
document.write( "250-20 = 230 MB<BR>\n" );
document.write( "C(230) = 0.06*230 + 20 = $33.80<BR>\n" );
document.write( "-------<BR>\n" );
document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
document.write( "--------  </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );