35 llamas live in an area that is 5 miles by 7 miies. What is the population density of the llamas?

The generic equation for density is mass/volume ([tex]D=\frac{ M}{V}[/tex]), in which the density is how much of one thing there is in a larger vessel.

In the context of this problem, the density is, statistically, how many llamas are in any given amount of area, where the "mass" is the number of llamas, and the "volume" is the area they inhabit:

First, we need to find the area that the 35 llamas are in, which can be found by multiplying the two sides of the area that are given, 5 and 7. This gives us an area of 35 square miles
Then, we divide the number of llamas (35) by the amount of space they are in (35), to get the density per square mile (1)

Therefore, the population density is 1 llama per square mile in this given area.

(Note that units are VERY important, as the are they are in must be square due to the fact that we are talking about area)