Station 1, Station, 2 and station 3 are three towns on a river which flows uniformly. Station 2 is equidistant from station 1 and station 3. A man rows a boat from station 1 to station 2 and back in 17 hours. He can row from station 1 to station 3 in 7 hours. Find the ratio between the speed of boat in still water to the speed of flow of water?
Station 1, Station, 2 and station 3 are three towns on a river which flows uniformly. Station 2 is equidistant from station 1 and station 3. A man rows a boat from station 1 to station 2 and back in 17 hours. He can row from station 1 to station 3 in 7 hours. Find the ratio between the speed of boat in still water to the speed of flow of water? Correct Answer 17 : 10
Given:
Time taken to travel from Station 1 to station 3 = 7 hours
Total time taken from station 1 to station 2 and back to station 1 = 17 hours
Station 2 is equidistance from station 1 and station 3
Formula used:
Speed = Distance / Time
Calculation:
Clearly man travels downstream from station 1 to station 3 because time consumed is lesser
Since flow is uniform, so journey between station 1 to station 3 can be described as :
Time taken between station 1 to station 3 = time taken from station 1 to station 2 + time taken from station 2 to station 3
7 = time taken from (station 1 to station 2 + station 2 to station 3) ---(i)
Since station 2 is equidistance from station 1 and 3
Therefore, time taken from station 1 to station 2 = time taken from station 2 to station 3
Therefore, 2 × time taken from station 1 to station 3 = 7
Time taken from station 1 to station 2 = 7 / 2 = 3.5 hours
Time taken from station 2 to station 1 = 17 - time taken between station 1 to station 2
= 17 - 3.5 = 13.5 hours
Let speed of boat in still water be ‘x’ and speed of current be ‘y’
Speed of boat in downstream = (x + y)
Speed of boat in upstream = (x -y)
(time taken to travel from station 1 to station 2) / (time taken from station 2 to station 1) = (3.5 / 13.5)
Since distance between station 1 and station 2 is fixed So time is inversely proportional to speed
(Speed of boat from station 2 to 1 (upstream)) / (speed of boat from station 1 to 2 (downstream)) = (3.5 / 13.5)
(x- y) / (x + y) = (3.5 / 13.5)
((x / y) -1) / ((x / y) + 1) = 3.5 / 13.5
Therefore, x / y = 17 / 10