Problema Solution
The speed of a stream is 3 mph. A boat travels 4 miles upstream in the same time it takes it to travel 10 miles downstream. What is the speed of the boat in still water?
Answer provided by our tutors
let
v = the speed of the boat in still water, v>0
s = 3 mph the speed of the stream
d1 = 10 mi traveling downstream
d2 = 4 mi traveling upstream
traveling downstream the speed of the boat is: v + s
traveling upstream the speed of the boat is: v - s
since speed = distance/time we have time = distance/speed we have
d1/(v + s) = d2/(v - s)
10/(v + 3) = 4/(v - 3)
by solving we find:
v = 7 mph
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the speed of the boat in still water is 7 miles per hour.