## Wednesday, September 28, 2011

### Anabelle's Blog Post: Surface Area

Recap/Review:

The day before yesterday we discussed whether or not a certain rectangular prism with a piece missing would have the same surface area as one that is whole. We came to the conclusion that it would.

When looking at them in one view/one face at a time it will be the same.

Today's notes:

We were asked if this figure was any different. Once we really thought about it, we found that it was. 2 small square units would be missed if we were to simply use the method for the last two figures.

With that in mind we easily solved the surface area for the figure:

SA= 2(lw)+P(h)+(lw)
= 2(2)(3)+10(2)+2(1)(1)
= 2(6)+20+2
= 12+22
= 34u^2

The next figure we inspected looked like this:

Once again, we figured out that the surface area for this one would also have a different surface area in comparison to one that is whole.

SA= 2(Top/bottom)+2(side)+2(front/back- missing units)+(inside)
= 2(lw)+2(lw)+2(s^2-s^2)+4(lw)
= 2(2)(3)+2(2)(3)+2(3^2-1^2)+4(1)(2)
= 12+12+2(9-1)+8
= 12+12+16+8
= 48u^2

Afterwards we discussed finding the surface area of a cylinder.

We were asked to make the net of a cylinder.

The circumference of one of the circles will give you the width/length of the rectangle that makes up the cylinder.

You can find the surface area of a cylinder using these formulas
SA= 2πr^2+2πrh
= 2πr^2+πdh
= 2πr^2+Ch

We then were given a cylinder to solve the surface area for. To make things different we were also asked to solve in pi. This means that we do not multiply anything by pi, but to simply leave it in to solve for later.

SA= 2πr^2+2πrh
= 2π5^2+2π(5)(12)
= 2π(25)+2π(60)
= π(50)+π(120)
= (170)π u^2 (solve by pi)

= 534.07 u^2 (solve to two decimals)

Homework:
• "Apply"
• number 22, 23: textbook
• 1.3 in the homework book and extra practice sheets
• Journal
Oh, and ....

That's right, Kim. I went there.

1. This comment has been removed by the author.

2. Great post Anabelle. I like how you added a lot of pictures. I also like how you used a blue font for the names of the shapes and a red font for the key words. Everything was well organized and easy to understand. Also, awesome picture at the bottem of the post.

3. Excellent post, Anabelle! It's good how you only used 2 colours to highlight the key words, instead of using various colours, to make it less distracting. The pictures were clear and easy to comprehend, and in short, everything was well organized. Good job.

4. good job annabelle :D i like your drawing at the last, lol. well, its a simple drawing but yeah it's looks nice and organized. good job :)

5. good job annabelle i like you use some coulor and picture of your own. and it was well organnized. keep it up

6. Nice post. First I have to say, your pictures were amazing. They showed the idea clearly and they were neat. You used colour well to highlight ideas. Nice picture at the end.

7. Great post Anabelle. You had a great organized layout, and I like the way you used only two colours to show important words. Your pictures were really well done, they were clear and it's unique that you drew them instead of making them on the computer. Also I like your picture at the end, very nice. :) Great job, keep up the good work. :)

8. Good job Anabelle!! I love your pictures they are very detailed and I also like how you explained what you were talking about.

9. Good post Anabelle ! I really like how you made the important parts of the pictures stand out, and you also made a really good picture at the end to show who would do the next post.

10. Good Job Anabelle! Your pictures were amazing it helped me understand better of what we did today, I liked how you used colors for important words, and the formulas for the surface areas were easy to understand especially with the pictures you drew, I also liked how you drew the picture instead of making it in the computer and also for adding the homework pages. Good Job Anabelle!

11. Good job Anabelle!! The pictures you made are amazing! I also like how you changed the font colour for the important words. Next time align the equal signs. Good job!

12. Good Job Anabelle! The pictures you made are very detailed which makes it easier to understand. Keep it up

13. Good job Anabelle. Your pictures are very easy to understand, and are very easy to identify. I also like how you changed the color around so that we can identify which are important words.

14. Great Job Anabelle! The picture's are really good! I like how you made your font's with different colours for key words. Your post is neat and it is very organized.

15. Ever cool Anabelle! The pictures were tremendous. I like how you explained this well. Nice finishing touch with the drawing, haha.

16. Great job Anabelle ! I liked how you took pictures of your work instead of making the pictures in paint. I also liked how you put colors in the words that are important. This post is very understandable and organized. Good job !