document.write( "Question 476024: A bus entered the Interstate and traveled at a constant speed of 42 mph. Two hours later a second bus followed the first bus, entering the Interstate from the same point as the first bus, and traveled at a constant speed of 66 mph. How long will it take the second bus to catch up with the first bus? \n" ); document.write( "
Algebra.Com's Answer #326444 by josmiceli(19441)\"\" \"About 
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How many miles head start does the 1st bus have?
\n" ); document.write( "\"+d%5B1%5D+=+42%2A2+\"
\n" ); document.write( "\"+d%5B1%5D+=+84+\" mi
\n" ); document.write( "Start a stopwatch when the 2nd bus enters interstate.
\n" ); document.write( "Both will now travel for the same amount of time
\n" ); document.write( "until bus 2 catches bus 1. Call this time \"t\".
\n" ); document.write( "---------------------
\n" ); document.write( "Let \"d\" = distance bus 2 has to go to catch bus 1
\n" ); document.write( "For bus 2:
\n" ); document.write( "(2) \"+d+=+66t+\"
\n" ); document.write( "For bus 1:
\n" ); document.write( "(1) \"+d-+84+=+42t+\"
\n" ); document.write( "----------------
\n" ); document.write( "Substitute \"d\" in (2) for \"d\" in (1)
\n" ); document.write( "(1) \"+66t+-+84+=+42t+\"
\n" ); document.write( "(1) \"+24t+=+84+\"
\n" ); document.write( "(1) \"+t+=+3.5+\"
\n" ); document.write( "It takes the 2nd bus 3.5 hrs to catch 1st bus
\n" ); document.write( "check:
\n" ); document.write( "(2) \"+d+=+66t+\"
\n" ); document.write( "(2) \"+d+=+66%2A3.5+\"
\n" ); document.write( "(2) \"+d+=+231+\"
\n" ); document.write( "and
\n" ); document.write( "(1) \"+d+-+84+=+42t+\"
\n" ); document.write( "(1) \"+231+-+84+=+42%2A3.5+\"
\n" ); document.write( "(1) \"+147+=+147+\"
\n" ); document.write( "OK \n" ); document.write( "
\n" );