document.write( "Question 512591: A ferry leaves a harbor and travels to a resort island at an average speed of 20 mph. On the return trip, the ferry travels at an average speed of 10 mph because of fog. The total time for the trip is 6 h. How far is the island from the harbor? \n" ); document.write( "

Algebra.Com's Answer #342662 by josmiceli(19441) $\"\"$ $\"About$

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Going to the resort island:
\n" ); document.write( "(1) $\"+d+=+20t%5B1%5D+\"$
\n" ); document.write( "Coming back:
\n" ); document.write( "(2) $\"+d+=+10t%5B2%5D+\"$
\n" ); document.write( "(3) $\"+t%5B1%5D+%2B+t%5B2%5D+=+6+\"$
\n" ); document.write( "Substitute (1) into (2)
\n" ); document.write( "(2) $\"+20t%5B1%5D+=+10t%5B2%5D+\"$
\n" ); document.write( "(2) $\"+t%5B2%5D+=+2t%5B1%5D+\"$
\n" ); document.write( "Substitute (2) into (3)
\n" ); document.write( "(3) $\"+t%5B1%5D+%2B+2t%5B1%5D+=+6+\"$
\n" ); document.write( "(3) $\"+t%5B1%5D+=+2+\"$
\n" ); document.write( "Plug this result into (1)
\n" ); document.write( "(1) $\"+d+=+20%2A2+\"$
\n" ); document.write( "(1) $\"+d+=+40+\"$
\n" ); document.write( "The island is 40 mi from the harbor
\n" ); document.write( "check:
\n" ); document.write( "(2) $\"+t%5B2%5D+=+2t%5B1%5D+\"$
\n" ); document.write( "(2) $\"+t%5B2%5D+=+2%2A2+\"$
\n" ); document.write( "(2) $\"+t%5B2%5D+=+4+\"$ hrs
\n" ); document.write( "and
\n" ); document.write( "(2) $\"+d+=+10t%5B2%5D+\"$
\n" ); document.write( "(2) $\"+d+=+10%2A4+\"$
\n" ); document.write( "(2) $\"+d+=+40+\"$
\n" ); document.write( "OK \n" ); document.write( "

\n" );