Transcript Shaded Area - Jamestown School District

Shaded Area
Find the area of the shaded region
How do I find the shaded area?
1. Find the area of the large or whole object.
2. Find the area of the small or inner object.
3. Use to find the shaded area (usually
subtract)
4. Make sure you answer the question!
Review Area Formulas
Rectangle:
A  bh
Triangle:
1
A  bh
2
Trapezoid:
1
A  (b1  b2)h
2
Circle:
A  r
2
Parallelogram:
A  bh
Example #1
Find the area of the blue region.
1010100
2
Area of Circle =  5  25
Area of Square =
Area of Square - Area of Circle =
100 25 
21.46
10
10
Example #2
Find the area of the red region.
Find the height of the trapezoid.
The height is 4.
Area of Trapezoid =
Area of Rectangle =
14
5
1
(14  8)4  44
2
8 4  32
Area of Trapezoid - Area of Rectangle =
44 - 32 =
12
8
Example #3
The sidewalk around a fountain is shown in green.
If it costs $2.25 per square foot to pour the sidewalk,
what will the total cost be?
 8  64
2
Area of the small circle =  3  9 
Area of the large circle =
2
8 ft
f
3 ft
Area of the large circle - Area of small circle =
64  9  55 
172.79
Answer the question!
$2.25  55 
$388.77
Today’s Review Questions
Answer true or false for each. If false, tell what is wrong.
1. I only need to find the area of one object for a shaded
area problem.
False
You need to find 2 areas.
2. The area of a parallelogram is the same as the area of
a rectangle.
Both are A=bh.
True
3. The height of a trapezoid is whatever the number on the
side is.
False The number on the side is the hypotenuse.
4. I can always use 3.14 instead of the  button.
False
For bigger numbers, the decimals will matter.