SOLUTION: A tour boat travels downstream and turns around and travels back upstream. Each trip is 20 miles, (40 miles total), the current is 5 miles per hour. The length of the tour in hours

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Question 820274: A tour boat travels downstream and turns around and travels back upstream. Each trip is 20 miles, (40 miles total), the current is 5 miles per hour. The length of the tour in hours is a function of the still water speed of the tour boat. Write a function and define the variable you use.
I'm having difficulty writing this into a function, as (to me) there are variables missing. I'm not a word problem person! haha Thank you so much for taking the time to help me!
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
When the boat goes upstream, the rate
of the current gets subtracted
--------------------
When the boat goes downstream, the
rate of the current gets added
--------------------
Let +s+ = the speed of the boat in still water
Let +t%5B1%5D+ = the time to go downstream
Let +t%5B2%5D+ = the time to go upstream
--------------------
Equation for going downstream:
(1) +20+=+%28+s+%2B+5+%29%2At%5B1%5D+
Equation for going upstream:
(2) +20+=+%28+s+-+5+%29%2At%5B2%5D+
--------------------
What you're looking for is +T+=+t%5B1%5D+%2B+t%5B2%5D+,
the time for the whole trip
--------------------
(1) +t%5B1%5D+=+20%2F%28+s%2B5+%29+
and
(2) +t%5B2%5D+=+20%2F%28+s-5+%29+
--------------------
+T+=+20%2F%28+s%2B5+%29+%2B+20%2F%28+s-5+%29+
+T+=+20%2A%28+1%2F%28s%2B5%29+%2B+1%2F%28s-5%29%29+
This is +T+=+f%28s%29+