SOLUTION: the speed of a stream is 3 km/hr. a boat travels 4 km upstream in the same time it takes to travel 10 km downstream. What is the speed of the boat in still water?
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Question 147415: the speed of a stream is 3 km/hr. a boat travels 4 km upstream in the same time it takes to travel 10 km downstream. What is the speed of the boat in still water?
Answer by aswathytony(47) (Show Source): You can put this solution on YOUR website!
let the speed of boat in still water is x km/hr.
given speed of stream is 3 km/hr.
then speed of boat upstream = ( x - 3) km/hr
speed of boat downstream = (x + 3 ) km/hr
Distance travelled upstream = 4 km
time taken to travel upstream = distance travelled upstream / speed of boat
upstream
= 4 / (x - 3 ) .............(1)
Distance travelled downstream = 10 km
time taken to travel downstream = distance travelled downstream / speed of boat
downstream
= 10 / (x + 3) ............(2)
given that boat takes same time to travel upstream and downstream.i.e; (1) & (2) are equal
i.e. 4/(x-3) = 10/ (x + 3 )
4 * (x +3 ) = 10 * (x- 3)
4x + 12 = 10x - 30
12 + 30 = 10x -4x
42 = 6x
x = 42 / 6 = 7.
i.e speed of boat in still water is 7 km/hr.
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