
Volume problem
A rectangle with vertices (0,0), (4,0), (4,6) and (0,6) is revolved about the xaxis to create a cylinder. What is the volume of this cylinder?
A. 32pi
B. 96pi
C. 144pi
D.288pi
E.NOTA (none of these above)
I'm thingking of NOTA. But it confuses me at the part where it says "revolved about the xaxis", i don't know if the way I understand it is correct, because if it's not then I definitely solved it wrong :P

The solution is:
$\displaystyle V=\pi r^2h=\pi \cdot 6^2\cdot 4=144\pi$.
Regards.
Fernando Revilla

I like this answer
Quote:
Originally Posted by
nhunhu9 C. 144pi
Taking a rectangle and revolving it around the xaxis certainly creates a cylinder.
Step 1. Draw the rectangle
Step 2. Draw the cylinder
Then using $\displaystyle V = \pi r^2h$ with $\displaystyle r=6, h = 4 \implies V = \pi\times 6^2\times 4 = 144\pi$

Thank you. I have another question, it sounds silly , but how to you know the radius is 6? I picture how a rectangle revolves around the x axis, and 6 looks like the circumference to me. Can you please explain?