Thursday, March 4, 2010

Asham Surface Area Growing Post

Rectangular Prism

I made this in Microsoft paint, so I gave it fake measurements if thats alright.

Net of Rectangular Prism also made in Microsoft Paint (tell me if somethings wrong because I always mess up the nets)

The formula you use to calculate the surface area of a rectangular prism is lxw (length x width). We will do this with all faces to get the area of each face, then add them together, which should give us the surface area.

5cm x 10cm = 50 cm2
5cm x 17cm = 85 cm2
10cm x 17cm = 170 cm2

50cm2+85cm2+170cm2 = 305 cm2

Triangular Prism

Heres is the shape

Here is the Net
The formula to calculate the surface area of a Triangular Prism is bxh÷2 (BASE X HEIGHT ÷ 2)

And heres the answer:
Rectangle = lxw
Rectangle = 2cm x 20cm
Rectangle = 40cm2

Triangle = bxh÷2
Triangle = 2cm x 5cm ÷ 2cm
Triangle = 5cm2

40cm2+5cm2 = 45cm2

Please tell me if I made a mistake, because I usually mess up with Triangular Prism's.

Now last but not least... the cylinder (-.-)
Net of a Cylinder here
Now we have the diameter, but we need to find the radius.
r = d÷2
r = 5 ÷ 2
r = 2.5cm

Now lets find the area of both circle(s)
A = pi x r x r
A = 3.14 x 2.5cm x 2.5cm
A = 19.625cm2 x 2 = 39.25cm2 (AREA OF BOTH CIRCLES)

Area of the Rectangle
A = lxw
A = (pi x d) x w
A = 3.14 x 5cm x 15cm
A = 235.50cm2

39.25cm2 + 235.50cm2 = 274.75cm2

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