document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1086496>Question 1086496</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The credit remaining on a phone card (in dollars) is a linear function of the total calling time made with the card (in minutes). The remaining credit after <BR>\n" );
document.write( "25<BR>\n" );
document.write( "minutes of calls is <BR>\n" );
document.write( "$26.50<BR>\n" );
document.write( ", and the remaining credit after <BR>\n" );
document.write( "53<BR>\n" );
document.write( " minutes of calls is <BR>\n" );
document.write( "$22.58<BR>\n" );
document.write( ". What is the remaining credit after <BR>\n" );
document.write( "61 minutes of calls ?<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #700701 by </B><A HREF=/tutors/aboutme.mpl?userid=mathmate><B>mathmate(429)</B></A><img src=\"/images/stars/stars-10.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=mathmate><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/cgi-bin/show-face.mpl?user=mathmate><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=700701\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Question:<BR>\n" );
document.write( "The credit remaining on a phone card (in dollars) is a linear function of the total calling time made with the card (in minutes). The remaining credit after <BR>\n" );
document.write( "25 minutes of calls is $26.50, and the remaining credit after 53 minutes of calls is $22.58. What is the remaining credit after 61 minutes of calls ?\r<BR>\n" );
document.write( "\n" );
document.write( "Solution:<BR>\n" );
document.write( "Given linear function, we have two given points of <BR>\n" );
document.write( "f(n), namely<BR>\n" );
document.write( "(25,26.50), (53,22.58)<BR>\n" );
document.write( "So apply the two point formula:<BR>\n" );
document.write( "slope m=(y1-y1)/(x2-x1)<BR>\n" );
document.write( "=(22.58-26.5)/(53-25)<BR>\n" );
document.write( "=-3.92/28<BR>\n" );
document.write( "=-0.14<BR>\n" );
document.write( " <BR>\n" );
document.write( "the equation required is<BR>\n" );
document.write( "(y-y1)=m(x-x1)<BR>\n" );
document.write( "y-26.5=-.14(x-25)<BR>\n" );
document.write( "simplify to get<BR>\n" );
document.write( "y=-0.14x+30<BR>\n" );
document.write( " <BR>\n" );
document.write( "The amount left after 61 calls<BR>\n" );
document.write( "A=f(61)=-0.14*61+30=21.46 </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );