A race boat
cover a distance of 66 km downstream in 110 minutes it cover the distance upstream in 120 minutes the speed of boat in still water is 34.5 km per hour find the speed of stream
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Let the speed of the stream or the streamflow be x km/hr.
When the racing boat is going downstream its speed is (34.5+x) km/hr and while going upstream its speed is (34.5-x) km/hr.
66/(34.5+x) = 110/60, or
110(34.5+x) = 66*60, or
(34.5+x) = 66*60/110 = 36, or
x = 36–34.5 = 1.5 km/hr.
Check: 66/(34.5-x) = 66/(34.5–1.5) = 66/33 = 2 hours or 120 minutes. Correct.
The streamflow is 1.5 km/hr.
When the racing boat is going downstream its speed is (34.5+x) km/hr and while going upstream its speed is (34.5-x) km/hr.
66/(34.5+x) = 110/60, or
110(34.5+x) = 66*60, or
(34.5+x) = 66*60/110 = 36, or
x = 36–34.5 = 1.5 km/hr.
Check: 66/(34.5-x) = 66/(34.5–1.5) = 66/33 = 2 hours or 120 minutes. Correct.
The streamflow is 1.5 km/hr.
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