Question
Speed of a boat in still water is three times the speed
of the boat in upstream. If the boat takes 20 minutes to cover 20 km in downstream, then find the speed of the boat in still water.Solution
Let speed of the boat in still water be ‘3x’ km/h. Speed of the boat in upstream = 3x ÷ 3 = ‘x’ km/h Speed of the stream = 3x – x = ‘2x’ km/h Speed of the boat in downstream = 3x + 2x = ‘5x’ km/h ATQ; (20/20) × 60 = 5x So, 5x = 60 Or, x = 12 So, speed of the boat in still water = 3 × 12 = 36 km/h
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