It is not entirely clear what the question is asking but the areas can be configured as80000 sq ft = 400 * 200 sq ft leaving an area of 400 * 200 sq ft, then 40000 sq ft = 400 * 100 sq ft leaving an area of 400 * 100 sq ft, then 10000 sq ft = 100 * 100 sq ft leaving an area of 300 * 100 sq ft, then 5000 sq ft = 100 * 50 sq ft leaving an area of 250 * 100 sq ft.
400 sq ft = 37.161 sq meters (rounded)
1 sq m = 10.76 sq ft, so 400/10.76 = 37.17 sq m
400 (sq feet) = 37.161216 sq meters
400 sq. miles = 27,878,400 sq. ft. x 100 = 2,787,840,000 sq. ft.
area of full circle = 400 sq. ft. if area = pi * radius2 then radius = square root ( area / pi ) = 11.284 radius (approx). = 22.568 diameter (approx).
16 ft * 25 ft = 16*25 = 400 sq ft.
1 sq. m = 10.7639 sq. ft.so: 400 sq. m. = (400 * 10.7639) 4305.56 sq. ft.
400.
1 square mile=640 acres, NOT 43,560 sq. ft. 43,560 sq. ft.= 1 acre. 1 sq. mi. =640x43,560 sq. ft.
I would say a 40,000 BTU furnace could big enough to heat a 400 SQ ft house, but where have you found a 400 SQ Ft house?
really big