Converting AAU's to Ounces

I have been looking at some lager recipes at Mayfair Court Brewhouse website. In some his recipes he gives the hop doses in AAU's. How would I convert AAU's to ounces?

AAU = Alpha Acid % (On hop Package) x Weight of hops (ounces)
A recipe calls for 10 AAU of Cascade
Your cascade says it's 5.0%, so to get 10 AAU, multiply the 5 by 2.
You need 2 ounces of cascade for that hop addition,if your hops were 4.0% you would need 2.5 ounces, if the AA% is 6.0 then you need 1.67 ounces.
etc.
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Or you could divide the AAU number bythe aa%of your hops. You get the same answer, it's just backward and would be easier if you needed say 42 aau's with a 9.7%aa hop.

Thanks much.