Tuesday, February 1, 2011

Surface area of a Cylinder

The base of a cylinder are circles, so first we have to review some basic termanology of circles:

-Half of diameter

-Cuts circle in half

-Perimeter of circle

-Ratio between circumfrence/diameter

Now we have to review the different formulas for circles:
radius= d/2=r
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...



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!


  1. Great job Sandra. Your post was very interesting and easy to understand. I liked how you explained how you got your answer step by step. Also this line "the base is the "circumfrence" the circles" I'm guessing there should be an "of" after circumference and you should also correct circumference.

  2. Wow, Sandra. You did a great job. Just by skimming through it I could see how much work you put into this. I think I saw circumference misspelled though, and like Paul said, a small grammar error. You explained things in great detail, and the pictures were carefully made too. The video was a nice touch as well, but I think you may have forgotten a link.

  3. Great job Sandra. Your work was really neat and organized. You explained a lot about cylinders and it shows all your hard work. I also like that you used your own pictures. I'm sure people will go to your blog to learn about cylinders. I think you forgot a link but other than that, great job.