The volume of a cylinder

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Question from Gonzalez, a student:

hi,
I have a problem, i need the formula to find the volume, area, surface area.
I have found that the are is pi X r^2, but i dont know how to find radius. if you
could help me, I'd be very happy.

Gonzalez,

In a cylinder a line across the circular end that passes through the centre of the circle is a diameter.

cylinder

The radius is half the length of a diameter. The height is as marked in the diagram. If r is the radius and h is the height then the volume of the cylinder is

r² h

I hope this helps,
Penny

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