Based on the problem statement, you can write the scale factor as
... 4 in : 5 ft
However, we suspect you are to convert this to the ratio of pure numbers (without units). We know 5 ft = 60 in, so this could be ...
... 4 in : 60 in, or
... 4:60, or
... 1:15.
The latter ratio is obtained by removing a factor of 4 from 4 and 60.
