Question 44

The ratio between speed of a boat downstream and speed of the boat upstream is 7 : 5 respectively. If the boat travels a distance of 63 km downstream in 3 hours, what is the speed of the boat in still water ? (in km/h)

Solution

Le the speed of boat be B km/hr and speed of river be R km/hr

Speed of boat in downstream = (B + R) km/hr

Speed of boat in upstream = (B- R)km/hr

It is given that $$\frac{B+R}{B-R}$$ = $$\frac{7}{5}$$

B = 6R...........(1)

Distance travelled downstream = 63 km

Time taken = 3 hr

63 = (B+R)3

B+R = 21 ..........(2)

From equation 1 and 2

R = 18 km/hr

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