a boat can travel 57 miles upstream against the current in the same amount of time it can travel 84 miles down stream with the current. if the boat's average speed in still water is 20 miles per hour. find the speed of the current​
Let
x -----> the speed of the current​
we have that
speed *time=distance
upstream
(20-x)t=57 --------> equation A
down stream
(20+x)t=84 -----> equation B
solve the system of equations
Adds the equation A and B
20t-xt=57
20t+xt=84
------------------
40t=141
t=3.525 hours
Find the value of x
(20+x)t=84
substitute the value of t
20+x=84/3.525
x=84/3.525 - 20
x=3.83 mph
therefore
the answer is
3.83 mph