Assuming the dirt is level with the top of the hole:
Volume = 2 x 4 x 3 = 24 cubic feet, or about 7/8 of a cubic yard.
6 cubic square
There is no dirt in a hole. If the hole is being dug, the amount of dirt being removed would be equal to the volume of the hole, which is 3 feet wide, 5 feet across, and 6 feet deep. So, the volume of dirt being removed would be 3 x 5 x 6 = 90 cubic feet.
cylinder 18 feet diameter x 1.5 feet deep volume = 381 cubic feet
The total volume of dirt which was in what is now a hole 3 feet long by 2 feet wide and 1 foot deep is 6 cubic feet. This same volume is now the amount of air which is in the hole. :-)
As it is a hole there is no dirt in it. However, a cylinder of dirt with radius 1.5ft, depth 5ft and a volume of πr2h ~= 35.34 cu ft has been removed.
None. It's a hole. 162 cubic feet of air. There is no dirt in a hole.
To calculate the volume of a cylinder one must multiply the area of the circle by the depth of the cylinder. The volume of the cylinder described is 98.172 cubic feet.
You are mixing volume (square yard) and area (length x width). How deep do you want the dirt? One foot deep you need about 80 square yards of dirt.
Without knowing the width of the shovel, it's not possible to calculate the volume of the hole. But whatever its volume is, there's no dirt at all in the hole.
There is no dirt. It's a hole.
There is no dirt in a hole that is 3 feet deep and six inches in diameter.
None, if you dug the hole, you emptied it of 162 square feet of dirt, so put it back.