I'm trying to find a number, I just can't wrap my mind around it to figure it out. Help needed.

If 5280' is a mile and equates to 1.0
If 1320' is .250
" 660' is .125
" 330' is .062

What would 383.08' be ? I came up .073. How far off is this ? Also what formula is used cause I can't remember how I came up with .073.   

Thanks in advance,
Cliff

Thank you, thank you. Maybe my mind isn't completely gone yet ?  Now I think I have a base # to work with on my motor / prop setups.

Again thanks for the formula,   

Cliff