document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=410403>Question 410403</A>: <I><SPAN STYLE=\"word-break: break-all;\"> In 1920, the record for a certain race was 45.7 sec. In 1990, it was 44.3 sec. Let R(t)= the record in the race and t= the number of years since 1920. So then what does R(t)=<BR>\n" );
document.write( "what is the predicted record for 2003?<BR>\n" );
document.write( "what is the predicted record in 2006?<BR>\n" );
document.write( "In what year will the predicted record be 43.74 seconds? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #288670 by </B><A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><B>ankor@dixie-net.com(22740)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><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=ankor@dixie-net.com><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=288670\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> In 1920, the record for a certain race was 45.7 sec.<BR>\n" );
document.write( " In 1990, it was 44.3 sec.<BR>\n" );
document.write( " Let R(t)= the record in the race and t= the number of years since 1920.<BR>\n" );
document.write( " So then what does R(t)=<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Find the slope of the equation Let yr 1920 = 0<BR>\n" );
document.write( "t1=0; r1=45.7<BR>\n" );
document.write( "t2=70; r2=44.3<BR>\n" );
document.write( ":<BR>\n" );
document.write( "m = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%2844.3-45.7%29%2F%2870-0%29 ALIGN=MIDDLE  ALT=\"%2844.3-45.7%29%2F%2870-0%29\"   DISABLED_style= \"max-width:90%; height:auto;\" > = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28-1.4%29%2F70 ALIGN=MIDDLE  ALT=\"%28-1.4%29%2F70\"   DISABLED_style= \"max-width:90%; height:auto;\" > = -.02 is the slope<BR>\n" );
document.write( "Find the equation<BR>\n" );
document.write( "r - 45.7 = -.02(t - 0)<BR>\n" );
document.write( "R(t) = -.02t + 45.7 is the equation<BR>\n" );
document.write( ":<BR>\n" );
document.write( "what is the predicted record for 2003?<BR>\n" );
document.write( "t = 83<BR>\n" );
document.write( "R(t) = -.02(83) + 45.7<BR>\n" );
document.write( "R(t) = 44.04 sec in 2003<BR>\n" );
document.write( ":<BR>\n" );
document.write( "what is the predicted record in 2006?<BR>\n" );
document.write( "t = 86<BR>\n" );
document.write( "R(t) = -.02(86) + 45.7<BR>\n" );
document.write( "R(t) = 43.98 sec in 2006<BR>\n" );
document.write( ":<BR>\n" );
document.write( "In what year will the predicted record be 43.74 seconds?<BR>\n" );
document.write( "Solve for t<BR>\n" );
document.write( "-.02t + 45.7 = 43.74<BR>\n" );
document.write( "-.02t = 43.74 - 45.7<BR>\n" );
document.write( "-.02t = -1.96<BR>\n" );
document.write( "t = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28-1.96%29%2F%28-.02%29 ALIGN=MIDDLE  ALT=\"%28-1.96%29%2F%28-.02%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "t = +98<BR>\n" );
document.write( "1920 + 98 = 2018, the predicted record of 43.74 </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );