Concrete can be purchased by the cubic yard. How much will it cost to pour a slab 18 feet by 18 feet by 6 inches for a patio if the concrete costs $42.00 per cubic yard?
The easiest thing to do is convert all the measurements to yards...
18ft = 6 yards
6 inch = 1/6 yard ( 6 inches = 1/2 ft.... so 1/6 yard) so the volume is
V = 6 x 6 x 1/6
Then all you do is calculate the cost. I hope this helps you out