Tuesday, October 5, 2010

Alvin's POOOST October 5, 2010

Hi people.

Today in math class each student was assigned t
o do a blog. Each blog is based on answering a question in the textbook, or on this paper he gave us !.

My question was on that sheet !.

The question is :The surface area of a metal tube must be coated with lubricant. The exterior diameter of the tube is 14 cm, the thickness of the tube wall is 4 cm, and the length of the tube is 50 cm. Determine the total surface area that must be coated, to the nearest tenth of a square centimeter.

The tube looked a little like :

First of I found out the total surface area of the cylinder

SA= 2pieR2 + 2pieRH
SA= 2 x 3.14 x 72 + 2 x 3.14 x 7 x 50
SA= 307.72 +2198
SA= 2505.72 cm

Then i found out the area of the empty circle

SA= 2pieR2
SA= 2 x 3.14 x 32
SA= 56.52 cm2

Then finally I took away
the area of the empty circles from the total surface area

- 56.52

The total surface area that would need to be coated would be 2449.20 cm2



  1. Good job Alvin! I'm so amazed that you actually got it right. Nice picture! You should've made the writings bigger though so we can see. :)

  2. Great job Alvin! Your explanation was very simple yet very understandable! Your picture was nice but you could've made the the writing a little bit bigger. You did the work correctly and neatly. You used the colours wisely but the font size was everywhere. Oh and you spelled 'pi' wrong. Other than that, nice job!