Mr. Sánchez owns a square field. The side lengths are 0.9 kilometers. There are 1,980 prairie dog burrows in the fields. What is the approximate density of prairie dog burrows in burrows per square kilometer?

The first thing we are going to do is find the area of the field. To do this we are going to use the area of a square formula: [tex]A=s^2[/tex]
Were 
[tex]A[/tex] is the area in square kilometers 
[tex]s[/tex] is one of the sides of the square
We know for our problem that  the side lengths of the field are 0.9 kilometers, so [tex]s=0.9[/tex]. Lets replace that value in our formula to find [tex]A[/tex]:
[tex]A=(0.9)^2[/tex]
[tex]A=0.81[/tex] 

Now, to find the population density of the filed, we are going to use the population density formula: [tex]P_{d}= \frac{I}{A} [/tex]
where
[tex]P_{d}[/tex] is the population density in in burrows per square kilometer
[tex]I[/tex] is the number of burrows 
[tex]A[/tex] is the are of the field
We know that [tex]I=1980[/tex] and [tex]A=0.81[/tex], so lets replace those values in our formula:
[tex]P_{d}= \frac{1980}{0.81} [/tex]
[tex]P_{d}=2444.4[/tex]

We can conclude that the density of prairie dog burrows is approximately 2444 burrws per square kilometer.