A metal conduit will be used as a pathway for wiring through a concrete block. The conduit is a 6 foot long rod with an outer diameter of 2.8 inches and an inner diameter of 2.6 inches. What is the volume of metal in the conduit in cubic centimeters?

Question

mathstudent55 · Answer

Do you know how to find the volume of a cylinder.

anonymous · Answer

2*pi*r

mathstudent55 · Answer

That is the circumference of a circle.
You need the volume of a cylinder.

anonymous · Answer

oh pi*r^2*h

mathstudent55 · Answer

Great.
All you need to do is find the volume of the outer dimension of the pipe, then find the volume of the inner dimension of the pipe and subtract.

mathstudent55 · Answer

|dw:1379387074682:dw|

anonymous · Answer

61.07 is my answer?

mathstudent55 · Answer

The outer cylinder has volume:
$V = \pi R^2h = \pi \left(\dfrac{D}{2}\right)^2h = \dfrac{\pi D^2h}{4}$

The inner cylinder has volume:
$V = \pi r^2h = \pi \left(\dfrac{d}{2}\right)^2h = \dfrac{\pi d^2h}{4}$

The voluyme of the hollow pipe is:

$V = \dfrac{\pi D^2h}{4} - \dfrac{\pi d^2h}{4}$

$V = \dfrac{\pi (D^2 - d^2)h}{4}$

mathstudent55 · Answer

You are correct that the volume is 61.07 cu in.
The question asks for the volume in $cm^3$.

anonymous · Answer

ok i got it now thank you so much

mathstudent55 · Answer

wlcm
What do you get in $cm^3$?

anonymous · Answer

1001 cm^3

mathstudent55 · Answer

Excellent!! Good job.