# Math Help - Volume of a cylinder

1. ## Volume of a cylinder

Hello, please help me refresh my memory, I need to figure out how much concrete an eight inch diameter by eight feet tube will hold. I remember the ....3.14 thing, but can't remember how to use it. Thanks!!!
ImReddy

2. ## Volume of a cylinder

8" diameter x 8'

First find the cross sectional area of the tube which is the area of the circle with 8" diameter and then multiply that area by the length of the tube.

The formula for the volume of a cylinder is $V = \pi*r^2*L$

so $V = \pi*(4in)^2*8ft$

lets convert everything to inches before we work it out

$V = \pi*(4in)^2*(8*12in)$

$V = \pi*16in^2*96in$

$\pi*1536in^3$

or roughly 4825.5 in^3 of cement

check out the google conversion tool