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Click
Name
LESSON
Here
Date
Class
Practice B
10-5 Circles
Use the circle to answer each question.
W
1. Name the circle.
2. Name two diameters.
V
X
Z
Y
3. Name four radii.
Find each missing value to the nearest hundredth.
Use 3.14 for !.
4.
5.
r ! 12 m
d ! 5 in.
C!
C!
22
Find the area of each circle. Use !7! for !.
6.
7.
r ! 21 yd
r ! 14 ft
A!
A!
8. The first Ferris wheel was built in 1893 in Chicago. Its diameter
was 250 feet. How many feet did the Ferris wheel rotate with
each complete turn? Use 3.14 for !.
9. Stonehenge, a circle of large carved stones in England, was
built more than 1,000 years ago. The circle of stones has a
diameter of 108 feet. About how many square feet of land does
22
Stonehenge cover? Use !7! for !.
Copyright © by Holt, Rinehart and Winston.
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46
Holt Middle School Math Course 1
Practice C
LESSON
10-5 Circles
Practice B
LESSON
10-5 Circles
Use the circle to answer each question.
1. Name the circle.
Use the circle to answer each question.
W
circle X
1. Label the center of the circle P.
2. Name two diameters.
X
V
Z
!W
Y
! and V
!Z!
Find each missing value to the nearest hundredth.
Use 3.14 for !.
Find each missing value to the nearest hundredth.
Use 3.14 for !.
4.
4.
5.
5.
C ! 87.92 in.
C ! 15.7 m
r ! 12 m
d ! 5 in.
15.7 in.
C!
d!
75.36 m
6.
28 in.
r!
2.5 m
22
Find the area of each circle. Use !7! for !.
22
Find the area of each circle. Use !7! for !.
6.
7.
7.
r ! 10 ft
d ! 8 yd
r ! 21 yd
r ! 14 ft
A!
616 ft2
A!
2
1,386 yd2
A!
2
314!7! ft2
A!
50!7! yd2
8. The diameter of a sandwich cookie is 1.75 inches. To the
nearest tenth, what is the combined area of the two wafer parts
of the sandwich cookie? Use 3.14 for !.
8. The first Ferris wheel was built in 1893 in Chicago. Its diameter
was 250 feet. How many feet did the Ferris wheel rotate with
each complete turn? Use 3.14 for !.
4.8 in2
785 feet
9. A circle of 50 flags surrounds the Washington Monument in
Washington, D.C. The diameter of the circle is about 238 feet.
About how far apart are the flags placed if they are evenly
9. Stonehenge, a circle of large carved stones in England, was
built more than 1,000 years ago. The circle of stones has a
diameter of 108 feet. About how many square feet of land does
22
22
Stonehenge cover? Use !7! for !.
spaced? Use !7! for ! and round to the nearest tenth of a foot.
9,164.57 square feet
about 15 feet
Copyright © by Holt, Rinehart and Winston.
All rights reserved.
46
Holt Middle School Math Course 1
To find the area A of a circle, use the formula A ! !r 2 and !7! for !.
A ! !r 2
A line segment with an endpoint at the center and an endpoint at
the circle is called the radius r. A line segment that passes through
the center and has both endpoints on the circle is called the
diameter d. The length of the diameter is twice the radius.
This is circle P.
QR
!
! is a diameter.
P
!Q
! and P
!R
! are radii.
22
" !7! • 42
22
" !7! • 16
Q
" 50.29 square units
The area is about 50.29 square units.
22
Find the area of each circle. Use !7! for !. Round each answer
to the nearest hundredth.
A
3. two radii
!B
A
! and A
!C
!
r!4
352
" !7!
R
P
Identify each part of the circle below.
!C
B
!
Holt Middle School Math Course 1
22
A circle is the set of all points in a plane that are the same distance
from a given point, called the center.
2. diameter
47
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All rights reserved.
Reteach
LESSON
10-5 Circles (continued)
Reteach
LESSON
10-5 Circles
1. circle
O
!Q
P
!, !
PR
!, and !
PO
!
!V
X
!, !
XW
!, !
XZ!, and !
XY
!
C!
P
R
3. Label point Q on the circle. Then name three radii.
Y
3. Name four radii.
Q
2. Draw and label its diameter R
!O
!.
B
A
C
6.
7.
The distance around a circle is called the circumference. The ratio of
the circumference of a circle to its diameter is always the same. This
relationship is called pi and is represented by the Greek letter !.
3
1
22
Pi is a decimal number that has no end and never repeats. 3.14 or !7!
is used to estimate pi.
To find the circumference C of a circle, use a formula.
d!6
A ! 28.29 square units
C ! !d
" 3.14 • 6
" 18.84
The circumference is about 18.84 units.
A ! 3.14 square units
8.
9.
5
2
Find the circumference. Use 3.14 for !.
4.
5.
d!8
d!4
C ! 25.12 units
Copyright © by Holt, Rinehart and Winston.
All rights reserved.
A ! 12.57 square units
A ! 78.57 square units
C ! 12.56 units
48
Copyright © by Holt, Rinehart and Winston.
All rights reserved.
Holt Middle School Math Course 1
Copyright © by Holt, Rinehart and Winston.
All rights reserved.
114
49
Holt Middle School Math Course 1
Holt Middle School Math Course 1