Question

a boat in upstream covers 110km in same time as it covers 140km in downstream find speed of stream is what percent of the speed of the boat in still water​

Answer 1

Let the speed of the boat be x km/h

Let the speed of the stream be y km/h

Upstream:

Speed = (x - y) km/h

Distance = 110 km

Time = Distance ÷ Speed

Time = 110 / (x - y)

Downstream:

Speed = (x + y) km/h

Distance = 140 km

Time = Distance ÷ Speed

Time = 140 / (x + y)

Given that the time taken is the same:

110/(x - y) = 140/(x + y)

110(x + y) = 140 (x - y)

110x + 120y = 140x - 140y

140x - 110x = 140y + 120y

30x = 250y

x = 25/3y

Find the percentage of the speed of the stream:

Percentage = (y ÷ 25/3y) x 100 = 12%

Answer: The speed of the stream is 12% the speed of the boat.