Question
A kayaker covers 64 km upstream and 96 km downstream in
8 hours and 6 hours, respectively. Find the time taken by the same kayaker to cover 140 km in still water.Solution
ATQ, Let speed of the kayaker in still water be ‘x’ km/h and speed of the stream be ‘y’ km/h Upstream speed of kayaker = (x – y) = (64/8) = 8 km/h --------- (I) Downstream speed of kayaker = (x + y) = (96/6) = 16 km/h ---------- (II) On adding equation (I) and equation (II), we have: 2x = 24 Or, x = 12 So, speed of the kayaker in still water = 12 km/h Therefore, time taken by the kayaker to cover 140 km in still water = (140/12) = 11.67 hours
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