Surface

1
Surface Area
2
Surface Area

• What does it mean to you?
• Does it have anything to do with what is in the
  inside of the prism.?
• Surface area is found the 7th grade way by
  finding the area of all the sides and then adding
  those answers up.
• How will the answer be labeled?

The area on the outside of the shape
Nope, the inside is volume
The 8th grade way uses a formula
Units2 because it is area!
3
7th Grade Rectangular Prism
How many faces are on here?
6
Find the area of each of the faces.
Do any of the faces have the same area?
A 5 x 4 20 x 2 40
If so, which ones?
B 6 x 5 30 x 2 60
C 4 x 6 24 x 2 48
Opposite faces are the same.
148 in2
Find the SA
4
8th grade SA

• You can find the SA of any prism by using the
  basic formula for SA which is
• Ph 2B SA
• P perimeter of the base
• h height(distance between the bases)
• B the base of the prism.

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8th grade Rectangular Prism
Total SA Ph2B
Find the perimeter (P) and area the base(B).
SAPh2B SA20 x 5 2x 24 SA100 48 SA48 in2
P 4646 20
B 4 x 6 24
h 5
6
7th Grade Cube
Are all the faces the same?
YES
A
How many faces are there?
4m
6
Find the Surface area of one of the faces.
4 x 4 16
Take that times the number of faces.
X 6 96 m2
SA for a cube.
7
8th Grade Cube
SA Ph2B
A
SA 16x4 2x16
4m
SA 64 32
P4444 16 h4 B4x4
96 m2
SA for a cube.
8
7th Grade Triangular Prism
How many faces are there?
4
5
5
How many of each shape does it take to make this
prism?
10 m
3
2 triangles and 3 rectangles SA of a triangular
prism
Find the surface area. Start by finding the area
of the triangle.
x 2 12
4 x 3/2 6
How many triangles were there?
5 x 10 50 front 4 x 10 40 back 3 x 10
30 bottom
2
Find the area of the 3 rectangles.
SA 132 m2
What is the final SA?
9
8th Grade Triangular Prisms

• Use the same triangular prism we used before.
  Lets use the formula this time. Ph 2B SA
• BE CAREFUL! Triangular prisms have a base of a
  triangle even if its laying on the rectangle.
• Find the perimeter of that same base and multiply
  it by the height of the prism. Find the area of
  the base, which is a triangle because it is a
  triangular prism. You will need two of them.
• Add those two things. Now you should have the
  same answer as before.
• Either way is the correct way.

10
8th Grade Triangular Prism
4
5
SA Ph2B
SA 12x102x6
10 m
3
SA 12012
P43512 h10 B ½ 3x46
SA 132 m2
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Cylinders
Only 8th grade
6
10m
Ph2B SA This time Pcircumference of the
base Since you were given the diameter choose the
Cpd formula
Ph (circumference x height)
3.14 x 6 18.84 x 10 188.4
3.14 x 9 28.26
2 B
X 2 56.52
Total SA
244.92
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SURFACE AREA

• Why should you learn about surface area?
• Is it something that you will ever use in
  everyday life?
• If so, who do you know that uses it?
• Have you ever had to use it outside of math?