When a ship goes down to B point from A point on a certain river, it will take 50 minutes.
When the same ship goes up from B point to A point, it will take 1 hour and 30 minutes.
How long does it take for the ball which dropped into this river at A point to be carried to B point?
Answer
3 hours 45 minutes
Solution
Distance from A to B is set to 450 of the least common multiple of 50 and 90.
Answer
3 hours 45 minutes
Solution
Distance from A to B is set to 450 of the least common multiple of 50 and 90.
The speed of going down is 450 / 50 = 9 and the speed of going up is 450 / 9 = 5.
The flow speed of the river is (9 - 5) / 2 = 2.
Therefore, the time to find is 450 / 2 = 225 minutes = 3 hours and 45 minutes.
