## Monday, March 8, 2010

### Elvin's Growing Post

Cylinder

How to find the TSA of a cylinder:

The cylinder has two circular bases.
The area of one circle is:
A = π × r2
A ≈ 3.14 × 0.3752
A ≈ 0.4415625
The area of the circle is
approximately 0.4415625 m2.

There are two circles, so the area
of both circles is approximately
0.883125 m2.

Calculate the total surface area.
S.A. ≈ 0.883125 + 5.652
S.A. ≈ 6.535125
The total surface area is approximately 6.54 m2

Rectangular Prism

How to find the TSA of a Rectangualar Prism:

Find the area of one circle.
A = π × r2
A ≈ 3.14 × 3.752
A ≈ 44.15625
The area of one circle is approximately 44.15625 cm2.
Find the area of two circles.
2 ×44.15625 = 88.3125
The area of both circles is approximately 88.3125 cm2.
Find the area of the rectangle using the circumference of the circle.
A = l × w
A = (π × d) × w
A ≈ 3.14 × 7.5 × 11
A ≈ 259.05

The area of the rectangle is approximately 259.05 cm2.
Calculate the total surface area.
Surface area = 88.3125 + 259.05
= 347.3625

Triangular Prism

How to find the TSA of a Triangular Prism:

a)
3 m
2.6 m
9 m

b) The bases of the prism are equilateral triangles.
The sides of the prism are rectangles.
3 m 3 m
9 m 2.6 m

rectangle triangle
A = l ×w A= (b × h) ÷ 2
A = 9 × 3 A = (3 × 2.6) ÷ 2
A = 27 A = 7.8 ÷ 2
A = 3.9
The area of one The area of one
rectangle is 27 m2. triangle is 3.9 m2.

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