document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1120830>Question 1120830</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Express commuter train #12 leaves the downtown station and travels at an average speed of 55miles per hour towards the north side station, which is 16miles away. Twelve minutes later, express commuter train #7 leaves the north side station and travels at an average speed of 45miles per hour towards the downtown station.\r<BR>\n" );
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document.write( "At the moment when the two trains pass each other, how far (in miles) is the #12 train from the downtown station and how long (in minutes) has the #12 train have been traveling? </SPAN>\n" );
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document.write( "Train #12 travels for 12 minutes (1/5 hour) at 55mph before train #7 starts; the distance train #12 travels in that time is (1/5)(55) = 11 miles.  So when train #7 starts, the trains are 16-11 = 5 miles apart.<br><BR>\n" );
document.write( "The combined speeds of the two trains is 100mph; together to travel those 5 miles requires 5/100 = 1/20 hour, or 3 minutes.<br><BR>\n" );
document.write( "So the trains meet when train #12 has been traveling for 12+3 = 15 minutes and train #7 has been traveling for 3 minutes.<br><BR>\n" );
document.write( "The ratio of the speeds of the two trains is 55:45 or 11:9, so train #12 travels 11/20 of those 5 miles and train #7 travels 9/20 of the 5 miles.  11/20 of 5 miles is 2.75 miles; so when the trains meet train #12 has traveled 11+2.75=13.75 miles.<br><BR>\n" );
document.write( "Answers: When the trains pass, train #12 is 13.75 miles from its starting point at the downtown station, and it has been traveling for 15 minutes. </SPAN>\n" );
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