SOLUTION: 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

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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?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Going to the resort island:
(1) +d+=+20t%5B1%5D+
Coming back:
(2) +d+=+10t%5B2%5D+
(3) +t%5B1%5D+%2B+t%5B2%5D+=+6+
Substitute (1) into (2)
(2) +20t%5B1%5D+=+10t%5B2%5D+
(2) +t%5B2%5D+=+2t%5B1%5D+
Substitute (2) into (3)
(3) +t%5B1%5D+%2B+2t%5B1%5D+=+6+
(3) +t%5B1%5D+=+2+
Plug this result into (1)
(1) +d+=+20%2A2+
(1) +d+=+40+
The island is 40 mi from the harbor
check:
(2) +t%5B2%5D+=+2t%5B1%5D+
(2) +t%5B2%5D+=+2%2A2+
(2) +t%5B2%5D+=+4+ hrs
and
(2) +d+=+10t%5B2%5D+
(2) +d+=+10%2A4+
(2) +d+=+40+
OK