A steel reinforcing rod is 12 ft. long and 1" thick in diameter. If a cubic foot of steel weighs 490 lb., how much does the rod weigh (to the nearest pound) ?

In cubic feet, the volume of the rod is given by the formula for the volume of a cylinder.

... V = (π/4) * d^2*h

... = (π/4) * (1/12 ft) ^2 * (12 ft)

... = π/48 ft^3

Then the weight is

... (490 lb/ft^3) * (π/48 ft^3) ≈ 32 lb