Scale : 1in is 100 miles
If you look at it as a fraction, where the distances on the map equal the actual distances, you get this:
1/0.5 = 100/x
x is the unknown, because you don't know what 0.5 in is equal to. From here, you can cross-multiply to get x.
1 * x = 100 * 0.5
x = 50 (because 0.5 = 1/2 and half of 100 is 50)
Therefore, 0.5in = 50 miles in real life.
A simpler way to think about it is like this:
1in = 100 miles
0.5in = ?
To get 0.5in from 1in, you divide by 2. That means to get from 100 to the ?, you also divide by 2 because the two equations are proportional.
100/2 = 50.
