GETE1102.pdf

5 cm
1. 216 cm 2
1 A B C D E
2 A B C D E
3 A B C D E
4 A B C D E
5 A B C D E
B C D E
6 cm
4 cm
Quick Check
5 cm
Test-Taking Tip
3 cm
A question could ask
for either surface area
or lateral area of a
solid. Read the
question carefully.
12 cm
Quick Check
1
2
2
EXAMPLE
Finding Surface Area of a Prism
Use a net to find the surface area of the prism at the left.
Surface Area = Lateral Area + area of bases
= sum of areas of lateral faces + area of bases
= (5 ? 4 + 5 ? 3 + 5 ? 4 + 5 ? 3) + 2(3)(4)
= 70 + 24
= 94
The surface area of the prism is 94 cm2 .
1 Use a net to find the surface area
of the triangular prism. See left.
You can find formulas for lateral and surface areas by looking at a net for a prism.
Perimeter of base
a � b � c � d d
c
d
c
Base
h
a b c d a b
h
a b c d
h
Perimeter Height
Lateral Area � ph
You can use the formulas with any right prism.
EXAMPLE
Using Formulas to Find Surface Area
Multiple Choice What is the surface area of the prism?
72 cm 2 78 cm 2 84 cm 2 96 cm 2
By the Pythagorean Theorem, the hypotenuse of the
triangular base is 5 cm.
L.A. = ph Use the formula for lateral area.
= 12 ? 6 p ≠ 3 ± 4 ± 5 ≠ 12 cm
= 72
The lateral area of the prism is 72 cm2 .
Now use the formula for surface area.
S.A. = L.A. + 2B
5 cm
6 cm
= 72 + 2(6) = 84 B ≠ (3 ? 4) ≠ 6 cm2 1
2
The surface area of the prism is 84 cm 2 . Choice C is the answer.
Use formulas to find the lateral area and surface area
of the prism.
432 m 2 ; about 619 m 2
Advanced Learners L4
After Example 2, ask students to write a formula for
the surface area of a rectangular prism with edges of
length