A 40 lb. bag of soil containing 2 cu.ft.3 will cover 25 sq.ft. @ 1" inch deep. My guess then would be 4 or more -40lb. bags would take care of 24 sq.ft. 4" deep.
50lb bags 3.7 60lb bags 3.1 80lb bags 2.3 90lb bags 2.1 These amounts are for using the redi-mix bags.
about 432 cubic inches
.21 yards of sand will fill an area 115 inches by 67 inches to a depth of 2.5 inches.
ABOUT 43 bags. Dry sand weighs ABOUT 100 lbs per cubic foot- and you need 21.3 cubic feet.
22/7x6x6x6 cubic inches
6,400 ft3
509.7 litres
To convert the weight of the sand into a volume and find out how much you need you would need to know the density of the sand as the more dense it is the less sand there will be in a 50lb bag and the more bags you would then need to fill the yard
29.45 cubic feet or 183.45 US gallons.
33.5 cubic feet.
259.2593 sq. yards.
You need 8 yards of sand that is 16 foot wide and 2 inches deep which is a volume of 8 x 16/3 x 2/36 ~= 2.37 cubic yards of sand.