document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=28163>Question 28163</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Jackie dives x distance at 50 miles per hour and returns over the same route at 40 miles per hour. What is her average speed for the round trip in miles per hour?<BR>\n" );
document.write( "A. 40.3<BR>\n" );
document.write( "B. 44.4<BR>\n" );
document.write( "C. 45.0<BR>\n" );
document.write( "D. 46.2<BR>\n" );
document.write( "E. 47.5<BR>\n" );
document.write( "I thought that when you figure the average in a problem you add up all the numbers and then divide by the amount of numbers there are. I believe that the answer should be (C). The answer they say is (B). Why? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #15357 by </B><A HREF=/tutors/aboutme.mpl?userid=Earlsdon><B>Earlsdon(6294)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Earlsdon><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=15357\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> To solve this problem, you will need to find \"weighted average\" speed.<BR>\n" );
document.write( "While it does seem that the average speed for Jackie's round trip ought to be <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%2850+%2B+40%29%2F2+=+45 ALIGN=MIDDLE  ALT=\"%2850+%2B+40%29%2F2+=+45\"   DISABLED_style= \"max-width:90%; height:auto;\" >, Jackie did not drive at the given speeds for equal amounts of time, so you must find the weighted average speed for the trip.<BR>\n" );
document.write( "Using the formula: <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d+=+rt ALIGN=MIDDLE  ALT=\"d+=+rt\"   DISABLED_style= \"max-width:90%; height:auto;\" > where: d = distance traveled, r = rate of travel (speed), and t = the time taken to travel the distance, d, you can find the weighted average speed by dividing the sum of the distances for each leg by the sum of the times taken for each leg. <BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28d1+%2B+d2%29%2F%28t1+%2B+t2%29 ALIGN=MIDDLE  ALT=\"%28d1+%2B+d2%29%2F%28t1+%2B+t2%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "The distance for each leg is given as x, so the sum for the trip is 2x.<BR>\n" );
document.write( "The times for each leg are not given so they must be calculated.  Using <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=d+=+rt ALIGN=MIDDLE  ALT=\"d+=+rt\"   DISABLED_style= \"max-width:90%; height:auto;\" > or <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+d%2Fr ALIGN=MIDDLE  ALT=\"t+=+d%2Fr\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t1+=+d1%2Fr1 ALIGN=MIDDLE  ALT=\"t1+=+d1%2Fr1\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t1+=+x%2F50 ALIGN=MIDDLE  ALT=\"t1+=+x%2F50\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t1+=+0.02x ALIGN=MIDDLE  ALT=\"t1+=+0.02x\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "----------------<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t2+=+d2%2Fr2 ALIGN=MIDDLE  ALT=\"t2+=+d2%2Fr2\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t2+=+x%2F40 ALIGN=MIDDLE  ALT=\"t2+=+x%2F40\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t2+=+0.025x ALIGN=MIDDLE  ALT=\"t2+=+0.025x\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
document.write( "\n" );
document.write( "Now we can find the weighted average speed (M) for the round-trip.\r<BR>\n" );
document.write( "\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=M+=+%28d1%2Bd2%29%2F%28t1%2Bt2%29 ALIGN=MIDDLE  ALT=\"M+=+%28d1%2Bd2%29%2F%28t1%2Bt2%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=M+=+%28x%2Bx%29%2F%280.02x%2B0.025x%29 ALIGN=MIDDLE  ALT=\"M+=+%28x%2Bx%29%2F%280.02x%2B0.025x%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=M+=+2x%2F0.045x ALIGN=MIDDLE  ALT=\"M+=+2x%2F0.045x\"   DISABLED_style= \"max-width:90%; height:auto;\" > Cancel the x's<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=M+=+2%2F0.045 ALIGN=MIDDLE  ALT=\"M+=+2%2F0.045\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=m+=+44.4 ALIGN=MIDDLE  ALT=\"m+=+44.4\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
document.write( "\n" );
document.write( "The aveage speed for the trip is 44.4 mph<BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );