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
2

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

2505.72
- 56.52
2449.20

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