Well, what you've got there is a unit conversion problem. You're told that 40' actual = 5.375" drawing. This means that the following is true:
To do a units conversion, you simply multiply by whichever of the correct factors above will cancel the units. You would like to know what 1' is? Well then, you need to cancel the feet in the numerator thus:
You probably don't have that many significant figures, so you'd probably say something like 1' actual = 0.1343" drawing. Does that make sense?