<PRE><B>Question 456043</B>
A motorboat traveled 60 miles with the flow of current for 90 minutes.
 The return trip against the current took 2 hours.
 What is the speed of the current in miles per hour?
:
Change 90 min to 1.5 hrs
:
Let s = speed of the boat in still water
Let c = speed of the current
Then
(s+c) = effective speed downstream
and
(s-c) = effective speed upstream
:
Write two distance equations, dist = time * speed
1.5(s+c) = 60
2(s - c) = 60
:
We can simplify both equations, divide the 1st eq by 1.5, divide the 2nd eq by 2, results
s + c = 40
s - c = 30
-------------addition eliminates c, find s
2s = 70
s = {{{70/2}}}
s = 35 mph is the boat speed in still water
:
Find c
35 + c = 40
c = 40 - 35
c = 5 mph is the current
;
:
Check solutions in the 1st original equation
1.5(35 + 5) = 
1.5(40) = 60 
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