Idea: The ship travels a certain distance from A to B, and the speed of traveling downstream must be faster than that of traveling upstream. This is because the speed of the ship downstream is: ship speed+water speed; Similarly, sailing against the current must not be faster, because the speed of sailing against the current is: ship speed-water speed. Among them, the ship speed and water speed are fixed.
1. Since the distance from A to B is certain, I assume that the distance between the two places is 48KM (the numbers can be written at will, which is convenient for calculation). Then the speed of sailing with the water is 8KM, and the speed of sailing against the water is 6KM. So:
Ship speed+water speed = 8km/h.
The ratio of ship speed to current speed = 6 kilometers per hour.
Visually, we can see that the ship speed is 7 and the water speed is 1.
It is concluded that the ship speed =7 water speed; Current speed = 1/7 ship speed
So it takes 48 hours to get from a to b at the speed of water.
2. Depart from A at 6 a.m. and arrive at B at 12. When the lifebuoy was found falling into the water, it had drifted to point B at the speed of water for a certain distance. It took 1 hour to find the lifebuoy on the return trip, and it took 1 hour for the lifebuoy to drift to point B at the speed of water. X hours later, I found the lifebuoy falling into the water.
Therefore, the distance from the water surface to the ground B= the first drift distance+1 hour drift+the return distance.
Downstream velocity 8*x= current velocity 1*x+ current velocity 1* 1+ downstream velocity 6* 1. T= 1. So the lifebuoy falls into the water 1 hour before reaching point B, that is 1 1.
Please draw with line segments, which will be more intuitive. This method was learned in primary school. I asked the second question three times before I figured it out.