The area of the small square is 1 cm^{ 2}. The widths of the corridors are
1cm. So the area of square ABCD is ___ cm^{ 2}.

ABCD can be divided into small squares which equal to
the given square. AD is 9 times the side length of the small square and is the
same as AB. So ABCD is 9 × 9 = 81 cm^{ 2}.