SOLUTION: 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 current moves at a rate of 9 km/hr?
Question 1121502: 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 current moves at a rate of 9 km/hr? Found 2 solutions by Alan3354, ikleyn:Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website! 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. Answer by ikleyn(52794) (Show Source): You can put this solution on YOUR website! .
The effective speed downstream is the sum of speeds
21 km/h + 9 km/h = 30 km/h. <<<---=== it is the speed relative to the river banks.
The time to travel 60 km downstream is = 2 hours.