## Thursday, February 25, 2010

### Althea's Surface Area Growing Post,

Three-Dimensional shapes

Rectangular Prism

This is what it would look like when you make the rectangular prism into a net:
To calculate the surface area of a rectangular prism is you have to:

1st: find the area of a rectangle -multilpy the length by width -A= l x w 2nd: find the total surface area -add all the areas
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A=l x w A=20 x 7 A=140 cm
TSA (Total Surface Area)= 140 + 24 + 24 = 188 cm ²
__________________________________________________________________ Triangular Prism
What it would look like when you make triangular prism into a net:
To calculate the surface area of a triangular prism is:

1st: find the area of a triangle -multiply base by height -divide by 2 -A= b x h /2 2nd: find the area of the rectangles -multiply length by width -A= l x w 3rd: find the total surface area -add all the areas ___________________________________________________________________

A= l x w A= 17 x 2 A= 34 mm²
TSA= 10 + 10 + 34 = 54 mm² ___________________________________________________________________ Cylinder
This is what it would look like if you make cylinder into a net:
To calculate the surface area of a cylinder is:

1st: find the circumference -If you have the diameter, what you have to do is multiply diameter by Ï€ (3.14) -Ï€d=circumference -If you have the radius, what you have to do is multiply 2 by the radius because 2 radius makes diameter. -2r=diameter -So you have the diameter, what you have to do next is find the circumference by multiplying diameter by 3.14 * You need to find the circumference because you'll need it to get the are of a rectangle * 2nd: to find the area of a circle -You need to find the radius of a circle -area=Ï€ x r x r 3rd: Find the area of the rectangle ___________________________________________________________________

area of the circle is 50.24 cm²
TSA= 266.64 + 50.24 + 50. 24 = 366.72 cm²