<PRE><B>Question 263749</B>
How far upstream can a motorboat travel at 8 mi/hr and still return downstream at 12 mi/hr in a total time of 4 hr?

let the time taken upstream be x
the down stream time will be 4-x hrs.

speed upstream = 8mph

distance upstream = 8*x

distance down stream = 12*(4-x)

8x= 48-12x
16x=48
x=3 hour---------------------------------- 24 miles
down stream time = 1hour

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