What are the formulas for downstream speed and upstream speed?
Still water speed (ship speed) = (downstream speed+upstream speed) ÷2.
Water velocity = (downstream velocity-upstream velocity) ÷2.
Running water problem, also known as running water problem, refers to the fact that when a ship sails in a river, it is driven or pushed by running water in addition to its own speed. In this case, calculate the speed, time and distance of the ship.
Example 1: A ship is traveling between A and B at a speed of 20km/h, and it takes 6 hours from A to B and 9 hours from B to A to find the current speed.
Analysis: this problem is set up as an ambush. The distance between A and B is always equal, whether downstream or upstream. If the current speed is x km/h, then the downstream speed is (20+x) km/h and the upstream speed is (20-x) km/h ... The enumerable equation:
6 (20+x) = 9 (20-x)，x = 4 (km/h)。
Ex. 2: The ship runs back and forth between the two docks at the same speed. It went down the river for 8 hours; Upstream, 10 hour. If the current speed is 3 kilometers per hour, find the distance between the two docks.
Analysis: If you want to find out the distance between the two docks, you can find out the distance between the two places on the premise of knowing the time, whether it is the downstream speed or the downstream speed; If you want to find out the speed along the water (against the water), you can solve the problem by finding out the ship speed when the water speed is known.
Let the ship speed be x km/h, and the equation can be listed as follows: 8(x+3)= 10(x-3), and x = 27 (km/h), then the distance between the two places is 8× (27+3) = 240 (km).