Please help!! problem with math?

Question

1.What is the weight of a concrete wall that is 25 feet long, 5 feet high and 8 inches thick? Assume concrete weighs 150 pounds per cubic foot. Round to the nearest pound. 

2.How many gallons of water will a rectangular tank hold if the base is a square that is 8 feet 10 inches on one side and the tank is 10 feet 3 inches high? Round to the nearest tenth.

Answer 1

1) Volume of the rectangular prism (V) = lbh

l = 25 feet , b = 8 inches , h = 5 feet

12 inches  = 1 ft

1 inch = 1/12

8 inch = 8/12

So b = 2/3 feet

V = 25 * 2/3 * 5

V = 250/3  ft^3

If 150 pounds for cubic feet

Then (250/3) * 150 = 12500

 Concrete weighs in the prism = 12500 pounds

2) Rectangular prism base is square, so it's length and breadths are same.

l = 8 feet 10 inches , b = 8 feet 10 inches 8 inches , h = 10 feet 3 inches

10 inches  = 10/12 = 0.83 ft

3 inches = 3/12  = 0.25 ft

l = 8.83 ft, b = 8.83 ft, h = 10.25 ft

V = 8.83 * 8.83 * 10.25 = 799.18 ft ^3

1 cubic feet = 7.48 gallons

799.18 ft^3 = 799.18 * 7.48

5978.28 gallons water will hold in the tank.