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.
