On a map, the distance between two historical markers is 4.5 inches, and 2.5 inches represents 10 miles. what is the actual distance between the historical markers?

4.5 / 2.5 = 1.8(10) = 18 miles

Hope that helps! :)

Inches / Miles: 

4.5 / x
2.5 / 10

Now, we can cross multiply to end up with:

2.5 * x = 4.5 * 10

Simplify:

2.5x = 45

Divide 2.5 on each side:

2.5x / 2.5 = 45 / 2.5

Simplify:

x = 45 / 2.5
x = 18

Awesome! Now we have a real ratio on the real distance of the markers.

2.5 : 10  &  4.5 : 18.

18 miles is the actual distance between the two markers.