Question 51

A motor boat,travelling at the same speed, can cover 25 km upstream and 39 km downstream in 8 hours . At the same speed it can travel 35 km upstream and 52 km downstream in 11 hours . The speed of the stream is

Solution

let speed of still water = x km/hr

speed of stream = y km/hr

According to the question,

$$ \frac{25}{x - y} + \frac{39}{x + y} = 8 $$.............(1)

$$ \frac{35}{x - y} + \frac{52}{x + y} = 11 $$ ..................(2)

solving (1) and (2)

x = 9

y = 4

therefore speed of stream = 4 km/hr

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