Question

if concrete weighs 160lbs per cubic ft, what is the weight of a concrete circular slab 4in thick and 15 ft across

Answer 1

Cubic ft l * w * h
160 = l * w * h

160 = 15 * w * 1/3 you have to put all of these in ft.

160 = 5w
w = 32 ft.

I assume you meant width and not weight.

Answer 2

its weight

Answer 3

OOPS sorry.. didn't read circular disregard what I wrote above.

Answer 4

cylinder = pi r^2 h
cylinder = 3.14 * (7.5)^2 * 1/3
cylinder = 58.875 ft^3

So it weighs 160 lbs for each ft^3 of concrete. You have 58.875 ft^3 so 160* 58.875 = 942 pounds.