The diameter of Earth, about 8,000 miles, is about 4 times the diameter of the moon. What is the approximate diameter of the moon?

The diameter of the moon is approximately 2,000 miles.

First, because we are solving for the approximate diameter of the moon, let's call the variable representing the diameter of the moon ##m##.

And let's call the diameter of the Earth ##e##.

The problem provides the relationship of the diameter of the Earth compared to the diameter of the moon. If equation for it can be written as:

##e = 4 xx m##

Because the diameter of the Earth (##e = 8000##) is provided we can substitute this into the formula and then solve for the approximate diameter for the moon which we called ##m## while keeping the equation balanced.

##8000 = 4 xx m##

##8000/4 = (4 xx m)/4##

##2000 = (4/4) xx m##

##2000 = 1 xx m##

##m = 2000##