The net free area of an opening combustion air from an directly from outdoors she be 1 square inch per 4000 btuh of the fuel burning appliances input ratings, therefore, a 160,000 appliance obtaining combustion air directly from outdoors would require a minimum opening of -------?

Is this a test? Are you testing us or are you taking a test

Get out the books and re-read, is all I know, since I don`t understand the question

This is homework, and that is how the question was written.

I would guess you would divide the total BTU`s (160,000) by the 1 sq inch per 4,000,, which would be 160,000 divided by 4,000,, total of 40 sq. inches