Name:
Area of a Circle
2
To find the area of a circle, use the formula pi x radius = area.
This formula is often written as A = πr 2 .
The circle pictured here has a radius of 5 cm.
5 cm
r = 5 cm
π ≈ 3.14
A = 3.14 x (5 cm x 5 cm)
A = 3.14 x 25 cm2
A = 78.50 cm2
Find the area of each circle. Use 3.14 for pi.
b.
a.
22
20 ft
c.
16 km
m
e.
34
in.
f.
50 cm
g. Jose has a circular dartboard. The bull’s eye
has a diameter of 14 mm. What is the area
of the bull’s eye?
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18 mi
d.
ANSWER KEY
Area of a Circle
2
To find the area of a circle, use the formula pi x radius = area.
This formula is often written as A = πr 2 .
The circle pictured here has a radius of 5 cm.
5 cm
r = 5 cm
π ≈ 3.14
A = 3.14 x (5 cm x 5 cm)
A = 3.14 x 25 cm2
A = 78.50 cm2
Find the area of each circle. Use 3.14 for pi.
b.
a.
22
20 ft
c.
16 km
m
1256 ft2
d.
375.94 m2
e.
in.
f.
50 cm
907.46 in.2
18 mi
34
803.84 km2
1962.50 cm2
1017.36 mi2
g. Jose has a circular dartboard. The bull’s eye
has a diameter of 14 mm. What is the area
of the bull’s eye?
3.14 x 49 mm2 = 153.86 mm2
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