Download Area of Circles and Sectors

Over Lesson 11–2
Find the area of the figure. Round
to the nearest tenth if necessary.
198 units2
A.
B.
C.
D.
A
B
C
D
Over Lesson 11–2
Find the area of the figure. Round
to the nearest tenth if necessary.
83.1 units2
A.
B.
C.
D.
A
B
C
D
Over Lesson 11–2
Find the area of the figure. Round
to the nearest tenth if necessary.
70 units2
A.
B.
C.
D.
A
B
C
D
Over Lesson 11–2
The area of a kite is 120 square meters. The length
of one diagonal is 15 meters. Find the length of the
other diagonal.
16 m
A.
B.
C.
D.
A
B
C
D
In this lesson we will:
• Find areas of circles.
• Find areas of sectors of circles.
• sector of a circle
• segment of a circle
Area of a Circle
MANUFACTURING An outdoor accessories
company manufactures circular covers for
outdoor umbrellas. If the cover is 8 inches longer
than the umbrella on each side, find the area of the
cover in square inches.
The diameter of the umbrella
is 72 inches, and the cover
must extend 8 inches in each
direction. So the diameter of
the cover is 8 + 72 + 8 or
88 inches. Divide by 2 to find
that the radius is 44 inches.
Area of a Circle
Area of a circle
Substitution
Use a calculator.
Answer: The area of the cover is about 6082 square
inches.
A swimming pool company
manufactures circular covers
for above ground pools. If the
cover is 1 foot longer than the
pool on each side, find the area
of the cover to the nearest
tenth of an foot.
314.2 ft2
A.
B.
C.
D.
A
B
C
D
Use the Area of a Circle to Find a Missing
Measure
ALGEBRA Find the radius of a circle with an area
of 58 square inches to the nearest tenth of an inch.
Area of a circle
Substitution
Divide each side by .
=r
4.3 ≈ r
Take the positive square
root of each side.
Simplify.
Answer: The radius of the circle is about 4.3 in.
ALGEBRA Find the radius of a circle with an area
of 45 square inches to the nearest tenth of an inch
3.8 in.
A.
B.
C.
D.
A
B
C
D
Area of a Sector
PIE A pie has a diameter of 9 inches and is cut
into 10 congruent slices. What is the area of one
slice to the nearest hundredth?
Step 1
Find the arc measure of a pie slice.
Since the pie is equally divided into
10 slices, each slice will have an arc
measure of 360 ÷ 10 or 36.
Step 2
Find the radius of the pie. Use this measure
to find the area of the sector, or slice.
The diameter is 9 inches, so the radius is
4.5 inches.
Area of a Sector
Area of a sector
x = 36 and r = 4.5
Use a calculator.
Answer: The area of one slice of pie is about
6.36 square inches.
PIZZA A pizza has a diameter of 14 inches and is
cut into 8 congruent slices. What is the area of one
slice to the nearest hundredth?
19.24 in2
A.
B.
C.
D.
A
B
C
D