MJ3
Ch 7.3 – Area of Complex Figures
Bellwork
1. The circular fountain in front of the courthouse has a
radius of 9.4 feet. What is the circumference of the
fountain? Round to the nearest tenth.
A=
πr2
A = 3.14(9.4)2
A = 3.14(88.36)
A = 277.4504
A = 277.5 ft2
You do not have to write the question
2
7
7
•
0
1
2
3
4
5
6
7
8
9
/
•
0
1
2
3
4
5
6
7
8
9
/
•
0
1
2
3
4
5
6
7
8
9
/
•
0
1
2
3
4
5
6
7
8
9
5
•
0
1
2
3
4
5
6
7
8
9
Assignment Review
• Circle worksheet
Before we begin…
• Please take out your notebook and get ready
to work…
• In today’s lesson we will look at the area of
complex figures…that is the area of
different shapes put together…
• The key here is that you calculate the area
for each figure and then add them
together…sounds simple…
Complex Figures
• A complex figure is made up of two or more
shapes…
• Examples:
Calculating Area
• To calculate the area of a complex figure
calculate the area of each figure and then
add the areas together.
• Since we are using more than one
formula...it is important that you continue to
use the formula method to keep the data
organized and calculate the correct answer
to the problem…
Example
• First…Identify the
shapes…in this case we have
a semi-circle and a rectangle
• You need to calculate the area
of each
• Notice that the diameter of
the semicircle is not given…
• You have to know the
characteristics of a rectangle
to know that the diameter of
the semi-circle is 15m.
• Additionally, you will need to
divide the 15 by 2 to get the
radius of the circle, which
you will need for the formula
of a circle.
7m
15 m
• Also, you will need to ½ the
area of the circle to get the
area of the semi-circle.
Area of Rectangle
A = ℓ●w
A = 15● 7
7m
A = 105 m2
Area of Semi-Circle
A = ½ πr2
A = ½ (3.14)(7.5)2
A = ½ (3.14)(56.25)
A = ½ (176.625)
A = (88.3125)
A = 88.3 m2
15 m
Area of Complex Figure
Rectangle = 105.0 m2
Semi-Circle = 88.3 m2
Total =
193.3 m2
Your Turn
• In the notes section of your notebook draw
and label the complex figure and then
calculate area using the formula method.
12 cm
6 cm
Comments
• Calculating the area of complex figures is
really simple…
• However, you have to be able to identify the
figures and know their characteristics…
• Also, it is important to be organized and use
the formula method…
• Finally, many students can do this,
unfortunately, the do not get the correct
answer because they forget to add the areas
together…
Summary
• In the notes section of your notebook
summarize the key concepts covered in
todaay’s lesson
• Today we discussed:
• Area of complex figures
• What is a complex figure and how do you
calculate the area?
Assignment
• Text p. 328 # 6 – 11
• This assignment is due tomorrow
• Make sure that you are showing how you get
your answer via the formula method (no work =
no credit)
• I do not accept late assignments