Question

Don is drawing a map with a scale of 1 in : 7 mi. He knows that the distance from his house to Fort Collins is 21 miles. How far apart should Don locate the two locations on his map?

Answer 1

So, you have a map scale of 1 in : 7 mi (which is also 1: 443520)

You can treat this like an algebra equation (see, there really *IS* a use for it!)

(1) 1 in = 7 mi

We have units of 7 mi and 21 mi, and we know that 7 is a factor of 21. 3 is the other factor. Thus:

(2) 7 * 3 = 21

Multiply both sides by 3

(3) 3 * 1 in = 3 * 7 mi

Simplify

(4) 3 in = 21 mi

Don should place the locations 3 inches apart on the map to indicate 21 miles in the real world.