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Geometry Surface Area of Rectangular and Triangular Prisms
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Geometry
Surface Area of Rectangular and
Triangular Prisms
Surface Area
Triangular prism – a prism with two parallel, equal triangles on opposite sides.
To find the surface area of a triangular prism we can add up the areas of the separate faces.
l
wh
Surface Area
In a triangular prism there are two pairs of opposite and equal triangles.
We can find the surface area of this prism by adding the areas of the pink side (A), the orange sides (B), the green bottom (C) and the two ends (D).
7 cm
5 cm2 cm
8 cm
AB
C
Surface Area
We should use a table to tabulate the various areas.
Example: Side Area Number of Sides
Total Area
A
B
C
D
Total
7 cm
5 cm2 cm
8 cm
AB
C
Surface Area
We should use a table to tabulate the various areas.
Example: Side Area Number of
Sides
Total Area
A 40 cm2
1 40 cm2
B
C
D
Total
7 cm
5 cm2 cm
8 cm
AB
C
Surface Area
We should use a table to tabulate the various areas.
Example: Side Area Number of
Sides
Total Area
A 40 cm2
1 40 cm2
B 10 cm2 1 10 cm2
C
D
Total
7 cm
5 cm2 cm
8 cm
AB
C
Surface Area
We should use a table to tabulate the various areas.
Example: Side Area Number of
Sides
Total Area
A 40 cm2
1 40 cm2
B 10 cm2 1 10 cm2
C 35 cm2 1 35 cm2
D
Total
7 cm
5 cm2 cm
8 cm
AB
C
Surface Area
We should use a table to tabulate the various areas.
Example: Side Area Number of
Sides
Total Area
A 40 cm2
1 40 cm2
B 10 cm2 1 10 cm2
C 35 cm2 1 35 cm2
D 7 cm2 2 14 cm2
Total
7 cm
5 cm2 cm
8 cm
AB
CD
Surface Area
We should use a table to tabulate the various areas.
Example: Side Area Number of
Sides
Total Area
A 40 cm2
1 40 cm2
B 10 cm2 1 10 cm2
C 35 cm2 1 35 cm2
D 7 cm2 2 14 cm2
Total 5 99 cm2
7 cm
5 cm2 cm
8 cm
AB
CD
Surface Area
Now you try...find the surface area!
Example:
C
BSide Area No of
SidesArea
Surface Area
Now you try...find the surface area!
Example:
C
BSide Area No of
SidesArea
2.0m
11.0m
2.1m
2.0m
Ex.2: Find the L.A and total surface area of Ex.2: Find the L.A and total surface area of the following triangular prism.the following triangular prism.
6cm
5cm
5cm12cm
LA = l•w
(5 x 12) = 60cm2
(5 x 12) = 60cm2
(6 x 12) = 72cm2
BA = BA = ½bh½bh
= ½(6)(4)= ½(6)(4)
= 12cm= 12cm22
x 2x 2
24cm24cm22
5
3
h
a2 + b2 = c2
h2 + 32 = 52
h = 4
6
192cm2
SA = LA + BA
= 192cm2 + 24cm2
= 216cm2
Find the surface area of the triangular prism.
12m² + 12m² + 63m² + 56m² + 21m² 9 m
S.A. = 164m²
