<PRE><B>Question 1121502</B>
A speedboat moves at a rate of 21 km/hr in still water. how long will it take someone to rise (?) the boat 60 km downstream if the rivers [sic] current moves at a rate of 9 km/hr?
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The speeds are added.
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d = r*t
t = d/r
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PS  Boats use knots, not km/hr.
21 km/hr = ~ 11.4 knots
Not much speed for a speedboat.  Beavers will be passing it.</PRE>