Question
A swimmer swims from point X upstream for 4 minutes.
Then he turns and swims downstream for 4 minutes and reaches point Y. If the distance between X and Y is 160 meters, find the speed of the stream in km/hr.Solution
ATQ,
Let speed of swimmer in still water be ‘s’ meters/minute and speed of stream be ‘w’ meters/minute. Speed upstream = s – w Speed downstream = s + w According to question: Distance between X and Y = distance downstream – distance upstream = 160 4 × (s + w) – 4 × (s – w) = 160 4s + 4w – 4s + 4w = 160 8w = 160 w = 160 / 8 = 20 m/minute Therefore, speed of stream = (20 × 60)/1000 = 1.2 km/hour
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