1. 1.3 Surface Area
Math 9

2. The sum of all the faces of an object
What is surface area?
The sum of all the faces of an object

3. Find the SA of each face and add them together.
When you have to find the surface area of a 3 dimensional object, there are 3 methods that you can choose to employ:
Find the SA of each face and add them together.
Use symmetry to group similar faces. Calculate area of one symmetrical face then multiply by the number of like faces.
Consider how the shape is made from its parts. Determine the SA of each part. Then remove the area of overlapping surfaces.

4. Remember: If you are dealing with a compound 3-D object (an object made up of two or more smaller ones), you must consider which of the faces will be included in the surface area (i.e. some faces will be covered).

5. Examples:
1) Find the surface area of each of the following objects. 4 cm 4 cm 9 cm f1
f1 = (4cm · 4cm) · 2 = 32 cm2
f2 = (4cm · 9cm) · 4 = 144 cm2
SA = 32cm2 +144cm2 = 176 cm2 f2

6. SA = 2 (area of circle) + (circumference x height) = 2 (πr2) + (2πrh)
1) Find the surface area of each of the following objects. 6 m height radius = 2.5 m
SA = 2 (area of circle) + (circumference x height)
= 2 (πr2) + (2πrh)
= 2π(2.5m)2 + 2π(2.5m)(6m)
= m m2 = m2

7. 2) What is the surface area of the following compound object?
Triangles
= 2(½ bh)
= 2(½·12m·9m) = 108 m2
Roof
= 2(15m x 10m)
= 300 m2
Front
= 2(12m x 8m)
= 192 m2
Side
= 2(8m x 10m)
= 160 m2 SA
= =760 m2
15 m
9 m
8 m
10 m
12 m

8. Warm-up Partner Practice P32 # 4b, 5b, 7, 13, 15,