1. Half the circumference
Notes Over
Area of Circles
Parallelogram
A = b h
radius
Half the circumference

2. Notes Over 10 - 3 Area of Circles A = p r2 A = p r2 A = 3.14 ( 3 )2
Find the area of each figure. 1.
3 in
20 m 2.
A = p r2
A = p r2
A = 3.14 ( 3 )2
A = 3.14 ( 10 )2
A = 3.14 ( 9 )
A = 3.14 ( 100 )
A = 28 in2
A = 314 m2

3. Notes Over 10 - 3 Area of Circles A = 12 ( 12 ) A = 144 cm2
Find the area of each figure.
12 cm 3.
12 cm
A = 12 ( 12 )
A = 144 cm2

4. Pg 517 10 – 3 #1 – 9, 10 – 27 A = p r2 A = p 32 A = p r2 A = 9 p in2
Find the area of each circle. Give an exact area and an approximate area to the nearest square unit.
1. r = 3 ft
2. d = 10 m
A = p r2
r = 5 m
A = p 32
A = p r2
A = 9 p in2
A = p 52
A = 25 p m2
A = 3.14 ( 9 )
A = 3.14 ( 25 )
A = 28 in2
A = 79 m2

5. Pg – 3 #1 – 9, 10 – 27
Find the area of each circle. Give an exact area and an approximate area to the nearest square unit.
3. r = 20 cm 4.
12 ft
A = p r2
A = p 202
A = 400 p cm2
A = 3.14 ( 400 )
A = p r2
= p 122
= 144 p ft2
A = 1256 cm2
A = 3.14 ( 144 )
A = 452 ft2

6. Pg – 3 #1 – 9, 10 – 27
Find the area of each circle. Give an exact area and an approximate area to the nearest square unit.
16 m 5.
60 cm 6.
A = p r2
= p 82
A = p r2
= p 302
= 64 p m2
= 900 p cm2
A = 3.14 ( 64 )
A = 3.14 ( 900 )
A = 201 m2
A = 2,826 cm2

7. Pg – 3 #1 – 9, 10 – 27
Find the area of each figure to the nearest square unit. 7.
10 in
3.5 in
7 in
+ 1/2p r2
= /2p 3.52
A = 70 + ½ (3.14) ( )
A =
= 89 in2

8. Pg – 3 #1 – 9, 10 – 27
Find the area of each figure to the nearest square unit. 8.
40 yd
40 yd
40 yd
+ p r2
= p 202
A = (3.14) ( 400 )
A =
= 2856 in2

9. Circle Pg 517 10 – 3 #1 – 9, 10 – 27 A = p r2 A = (2) (2) A = p 22
9. Which has a greater area, a circle with radius 2 m or a square with side length 2 m? Explain.
2 m
2 m
A = p r2
A = (2) (2)
A = p 22
A = 4 in2
A = (3.14) ( 4 )
Circle
A = in2

10. Pg – 3 #1 – 9, 10 – 27