http://www.ck12.org Chapter 10. Perimeter and Area
- Find the diameter of a circle with area 36π.
- Find the area of a circle with diameter 20 inches.
Answers:
- The area of the shaded region would be the area of the square minus the area of the circle.
A= 102 − 25 π= 100 − 25 π≈ 21. 46 cm^2- First, use the formula for the area of a circle to solve for the radius of the circle.
A=πr^2
36 π=πr^2
36 =r^2
r= 6If the radius is 6 units, then the diameter is 12 units.
- If the diameter is 20 inches that means that the radius is 10 inches. Now we can use the formula for the area of a
circle.A=π( 10 )^2 = 100 πin^2.
Practice
Fill in the following table. Leave all answers in terms ofπ.
TABLE10.2:
radius area diameter- 2
- 16 π
- 10
- 24
- 9
- 90 π
- 35
8.^7 π - 60
- 36 π
Find the area of the shaded region. Round your answer to the nearest hundredth.
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15.- Carlos has 400 ft of fencing to completely enclose an area on his farm for an animal pen. He could make the
area a square or a circle. If he uses the entire 400 ft of fencing, how much area is contained in the square and
the circle? Which shape will yield the greatest area?