Final answer:
To find the population density, divide the population by the area of the quadrilateral.
Step-by-step explanation:
To find the population density, we need to divide the population by the area. In this case, the population is 1,500,000 and the area is the area of the quadrilateral. Since each unit on the grid represents 1 mile, we can calculate the area of the quadrilateral using the length and width.
Let's say the length of the quadrilateral is x miles and the width is y miles. Then, the area is equal to x * y. To find the population density, we divide the population by the area: population density = population / area = 1,500,000 / (x * y).
Since the question does not provide the length and width of the quadrilateral, we cannot calculate the exact population density. However, if you provide the length and width, we can help you calculate it.