Composite Figures
• A composite figure
• Finding the area of
is made up of two or
composite figures
more shapes.
requires finding the
sum of the areas of
figures that compose
it.
1. Before applying
formulas, you should
break up composite
figures into polygons.
Formulas that can
be applied:
Triangles: A = ½bh
Square: A = s² or L • W
2. Apply the formula for
the area of each
polygon.
Rectangle: A = L • W
Trapezoid: A = ½h(b₁ + b₂)
3. Find the sum of the
areas of the polygon.
Parallelogram: A = bh
Surface Area
The surface area of a three-dimensional
figure is the sum of the areas of its
surfaces.
To help you see all the surfaces of a threedimensional figure, you can use a net.
A net is the pattern made when the
surface of a three-dimensional figure is
layed out flat showing each face of the
figure.
Finding Surface Area
Find the surface area of the
Area of Cube: 54cm²
3-by-3-by 3 cube. Then find
the area of the cube with
Area of Cube with
one missing corner. (Unit of
missing
corner:
54 cm²
measure = cm)
How does the missing
cube at the vertex change
the surface?
Removing the unit cube from the
vertex creates an inverted corner
on the cube. The surface area did
not change.