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