Perimeter and Area of Composite Figures
The figure to the right is a composite figure.
How would you define a composite figure?
A composite figure consists of two or more basic shapes or figures.
Example 1: a) How would you calculate the area of this figure?
The diameter of the circle is 50 cm.
The area is approx.. 3768.25 cm2
b) How would you calculate the perimeter of this figure?
Circumference of a circle = 2π r
r-radius
r=25 cm
d=50 cm
P=Prectangle+Circumfrencesemi-circle
=95+50+95+2 π252
=240+25 π
=240+78.54
=318.54
The perimeter of the figure is approx. 318.54 cm.
Example 2: Determine the area and the perimeter of the following shape, to the nearest tenth of a metre.
Solution: r=3 m
A=A1+A2+A3
=Asemi-circle+Arectangle+Atrapezoid
Arectangle=l ×w
=18 ×4
=72
l=18 m
w=4 m
Atrapezoid=b1+b2×h2
A=14.14+72+36
=122.14
The area pf the above figure is approx.. 122.14 m2
In order to find the perimeter, we need to find x.
32+42=x2
9+16=x2
25=x2
x=5 m
P=5+6+5+3+4+6+232+6+4+3
=42+3
=42+9.42
=51.42
The perimeter of the shape is approx.. 51.42 m
