For this case the first thing you should know is the following change of units:
1Km = 1000m
We have then:
250 meters = 0.250 km.
The number of fences will be given by the quotient between the total length of the route and the spacing between each fence.
We have then:
N = (15) / (0.250)
N = 60
Answer:
60 fences will be installed throughout the project.
