## Tuesday, February 1, 2011

### Surface area of a Cylinder

Cylinders
The base of a cylinder are circles, so first we have to review some basic termanology of circles:
-Diameter
-Circumfrence
-Pi

-Half of diameter

Diameter
-Cuts circle in half

Circumfrence
-Perimeter of circle

Pi
-Ratio between circumfrence/diameter
-3.14

Now we have to review the different formulas for circles:
Cicumfrenc=∏.d=c
diameter= 2.r or c/∏=d
Area of a circle= ∏.r.r

Net of a Cylinder:

This is a net of a cylinder:

-The height is always given to you

-the base is the circumfrence the circles

-To calculate the surface area you have to add up the lateral area (LxW) and other formulas such as...

LxW

∏.r.r=A
d=2r
R=d/2
C=∏.d

For now, We are going to practice how to calculate the area, circumfrence, diameter, and radius of a circle. For these five circles, I had to calculate the area and circumfrence using the given radius or diameter. I had to plug in the given information into the formulas to find the area and circumfrence. This is how I did it.

For circle A and B, we have the given circumfrence but we have to find the radius, diameter and area. So what I did first was I found the diameter because once you have found the diameter or radius, you can find anything. I found the diameter by dividing the circumfrence by pi (3.14) and that gave me the diameter, then I could find the radius and area.

Here's a video on Surface area of Cylinders:

I hope you understand more about circles and cylinders, please notify my if I made any mistakes or if you have any suggestions for my post. Thanks!