Population density is the number of individuals per unit area. To calculate the population density, number of individuals is divided by the size of the area. Therefore, in the given question Population Density = Number of mice / garden area. The number of mice is 168 and area of the garden is 12×7 = 84 square meter. Thus, population density of mice = 168/ 84 = 2
Placer mining can be less damaging to the environment than surface mines, as the sediment is returned to the water after the minerals have been extracted.
