document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=930651>Question 930651</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A child is running on a moving sidewalk in an airport. When she runs against the sidewalk's motion, she travels <BR>\n" );
document.write( "40ft<BR>\n" );
document.write( " in <BR>\n" );
document.write( "8<BR>\n" );
document.write( " seconds. When she runs with the sidewalk's motion, she travels <BR>\n" );
document.write( "90ft<BR>\n" );
document.write( " in <BR>\n" );
document.write( "10<BR>\n" );
document.write( " seconds. What is the rate of the child on a still sidewalk and what is the rate of the moving sidewalk? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #565240 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=565240\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A child is running on a moving sidewalk in an airport.<BR>\n" );
document.write( " When she runs against the sidewalk's motion, she travels 40ft in 8 seconds.<BR>\n" );
document.write( " When she runs with the sidewalk's motion, she travels 90ft in 10 seconds.<BR>\n" );
document.write( " What is the rate of the child on a still sidewalk and what is the rate of the moving sidewalk?<BR>\n" );
document.write( ":<BR>\n" );
document.write( "let c = child's normal running rate, (ft/sec)<BR>\n" );
document.write( "let w = sidewalk moving rate<BR>\n" );
document.write( "then<BR>\n" );
document.write( "(c-s) = effective rate running against the sidewalk<BR>\n" );
document.write( "and<BR>\n" );
document.write( "(c+s = effective rate running with the sidewalk<BR>\n" );
document.write( ":<BR>\n" );
document.write( "Write two distance equations, one for each way, dist = rate * time<BR>\n" );
document.write( "8(c-s) = 40<BR>\n" );
document.write( "10(c+s)= 90<BR>\n" );
document.write( "simplify, divide the 1st eq by 8, the 2nd by 10 and we have<BR>\n" );
document.write( "c - s = 5<BR>\n" );
document.write( "c + s = 9<BR>\n" );
document.write( "---------- addition eliminates s, find c<BR>\n" );
document.write( "2c = 14<BR>\n" );
document.write( "c = 14/2<BR>\n" );
document.write( "c = 7 ft/sec is the child's running speed<BR>\n" );
document.write( "Find s<BR>\n" );
document.write( "7 + s = 9<BR>\n" );
document.write( "s = 9 - 7<BR>\n" );
document.write( "s = 2 ft/sec, is the rate of the sidewalk<BR>\n" );
document.write( ":<BR>\n" );
document.write( ":<BR>\n" );
document.write( "See if this checks out in the 1s original equation<BR>\n" );
document.write( "8(7 - 2) = 40<BR>\n" );
document.write( "8(5) = 40 </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );