Question
Speed of a boat in still water is 25% less than its
downstream speed. If the upstream speed of the boat is 24 km/h, find the downstream distance covered by the boat in 150 minutes.Solution
Let the speed of boat in still water be 'v' km/h and speed of stream be 'y' km/h
v = 0.75 × (v + y)
Or, 4v = 3v + 3y
Or, v = 3y
Upstream speed of boat = 3y − y = 2y km/h
So, 2y = 24
Or, y = 12
Downstream speed of boat = 3y + y = 4y = 4 × 12 = 48 km/h
Required distance = 48 × (150 ÷ 60) = 120 km
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