Question
The ratio of the speed of boat in upstream to speed of
boat in downstream is 7:9. If the boat can cover a total of 70 km upstream and 144 km downstream in 13 hours, then find the time taken by the boat to cover 180 km in still water.Solution
Let speed of boat in upstream and downstream be ‘7x’ km/h and ‘9x’ km/h respectively. 70/7x + 144/9x = 13 10/x + 16/x = 13 26 = 13x x = 2 Speed of boat in still water = (7x + 9x)/2 = 8x = 8 × 2 = 16 km/h Desired time = 180/16 = 11.25 hours
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