A cy is 27 cubic feet. If you divide 27 by 0.33 (4 inches in feet).

The result is 81.8 square feet. Any shape (volume) of 81.8 sf, 4 inches deep could be filled with 1 cy of concrete.

For example, 1 foot by 81.8 feet. Or 2 feet by 40.9 ft. Or the square root of 81.8 is about 9.

So 9 x 9 x 0,33 rounded off is 27 cubic feet

The result is 81.8 square feet. Any shape (volume) of 81.8 sf, 4 inches deep could be filled with 1 cy of concrete.

For example, 1 foot by 81.8 feet. Or 2 feet by 40.9 ft. Or the square root of 81.8 is about 9.

So 9 x 9 x 0,33 rounded off is 27 cubic feet