Final answer:
Joe and Mary can add up to 462.5 square feet to their home as per the local zoning law limiting building size to 25% of their property area, after considering the current building cover.
Step-by-step explanation:
Joe and Mary's maximum allowed building size under local zoning laws can be calculated by first determining the total area of their lot and then applying the 25% building limit. The total lot area is the product of the lot's dimensions which is 75 feet by 110 feet.
To compute this, multiply 75 by 110 to get 8,250 square feet as the total lot area. Then, to find 25% of that, we compute 8,250 square feet × 0.25 which equals 2,062.5 square feet. This is the total allowable building size on their lot under the zoning regulations.
Since their home and garage already cover 1,600 square feet, the remaining square footage they can add is found by subtracting 1,600 from 2,062.5. Therefore, 2,062.5 square feet - 1,600 square feet equals 462.5 square feet.
The maximum square footage of floor area that Joe and Mary can add to their home is 462.5 square feet.