Answer:
We need to calculate how many times there are 800 meters on 5000 meters.
To know so, we can divide 5000 by 800:
5000/800 = 6.25
So now, we know there are 800 meters 6.25 times on this trail.
So, how many markers have to be used? There have to be used 6, as the other 0.25 times will be the last 200 meters of the trail (800*0.25) and we only have to put a mark each 800.
We can also do this manually, from the start:
First mark would be at 800, next at 1600, next at 2400, next at 3200, next at 4000 and the last one at 4800. As we have said, 6 markers.