A man rowing a boat at the rate of 5 km an hour in still water takes thrice as much time in going 40 km up the river as in going 40 km down. find the rate at which the river flows.
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Time upstream = 3 times time downstream
Time ratio Upstream : downstream = 3 : 1
Hence speed ratio
Upstream speed : downstream speed = 1 : 3
Speed of boat = 5 km/hr
Speed of stream = y km/hr
Given 5 - y/5+y = 1/3
3*(5-y) = 5+y
15 - 3y = 5+y
10 = 4y
y = 2.5 km/hr
Hence speed of stream(river flow) = 2.5km/hr
Time ratio Upstream : downstream = 3 : 1
Hence speed ratio
Upstream speed : downstream speed = 1 : 3
Speed of boat = 5 km/hr
Speed of stream = y km/hr
Given 5 - y/5+y = 1/3
3*(5-y) = 5+y
15 - 3y = 5+y
10 = 4y
y = 2.5 km/hr
Hence speed of stream(river flow) = 2.5km/hr
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