how much concrete for 30x40?

Question

Update:

How much concrete would I need for a 6 in by 30x40 slabe

Answer 1

That depends on how thick you want the slab (note the spelling) to be.  Did you play hooky in the third grade when they learned about finding volumes of solids?

Answer 2

As much as it takes for "LANGUAGES", doofus.

Answer 3

Depends on the thickness which is determined by the usage.  Do you need to pour footings?   Will it be a basement slab or a driveway??

30 ft x 40 ft is 1200 square feet, if the slab is 1 foot thick it is  1200 cubic feet divide by 27 cubic feet = 44.44 yards,  if 6 inches thick it would be 22.22   cubic yards