A ratio is the same thing as a fraction.
You should have [tex]\frac{1 in.}{50 mi.}[/tex]
If you want to make something in inches, but the miles are on the bottom, you will have to multiply the miles on top to get rid of it on the bottom,
Like this: [tex]\frac{1 in.}{50 mi.} . \frac{450 mi.}{1 in.} [/tex]
That makes it 450/50, which is just 9 inches.
The answer is 9 inches.
