a race is 10kilometers long. the markers will be placed at the begining and end of of the race coarse and at each 500 meter mark. how many markers are needed to mark the course for the race?
Draw a diagram and make the problem similar and simpler.
1 km=1000 m, 10 km=10,000 m
If the race were 500 m you would need one at the beginning and one at the end, for a total of 2.
If the race were 1000 m, you would need one at the beginning, one at the end, and one in the middle. (1000/500)+1=2+1=3
If the race were 1500 m, you would have (1500/500)+1=3+1=4
If the race were 2000 m, (2000/500)+1=4+1=5
Again, make a similar, simpler problem and look for a pattern.
Now you can see the pattern and solve the problem: (10,000/500)+1=20+1=21 markers