NAME ____________________________________________ DATE _____________________________ PERIOD _____________
Practice 7.9(B)
SCORE __________
Determine the circumference and area of circles.
Multi-Step Example
Mary has a charm bracelet that creates a circle with an area of 3.8 square inches. If each charm on
the bracelet is 0.25 inch wide, approximately how many charms can Mary put on the bracelet?
A = π𝑟 !
Area of a circle
3.8 ≈ 3.14𝑟 !
!.!
!.!"
Substitute 3.8 for A and 3.14 for π.
≈ 𝑟 !
Divide both sides by 3.14.
1.1 ≈ r
Take the square root of both sides.
Round to the nearest tenth.
The radius is 1.1 inches, so the diameter is 2 • 1.1 or 2.2 inches.
Next, find the circumference.
C = πd
Circumference of a circle
C ≈ 3.14 • 2.2
Substitute 3.14 for π and 2.2 for d.
C ≈ 6.908
Multiply. Finally, divide the circumference by the width of each charm:
So, Mary can put 27 charms on the bracelet.
1 Joe’s Coffee is having a stained glass window installed
on their front door. Approximately how much glass
will be needed to create the stained glass window? Use
3.14 for π.
!.!"#
!.!"
= 27.632.
2 The street signs in a subdivision are in the shape of
circles. Each street sign has an area of 452.16 square
inches. What is the approximate circumference of each
sign? Use 3.14 for π.
F 38
G 72
H 75
J 144
3 Elaina’s old bicycle had tires with a 12-inch diameter.
Her new bicycle has tires with a 16-inch diameter.
What is the difference in the circumference of the
tires? Use 3.14 for π
A 2.4 ft !
B 9.6 ft !
C 11 ft
A 12.56 in.
!
29.14 in.
C 37.68 in.
D 38.5 ft !
D 50.24 in.
Course 2 • Expressions, Equations, and Relationships TX101 NAME ____________________________________________ DATE _____________________________ PERIOD _____________
Practice 7.9(B) (continued)
SCORE __________
4 Kim has two circular push pins on her bulletin board.
The table shows the diameter length of each pin. What
is the difference in area between the two push pins?
Use 3.14 for π.
Size of Pin
Large
Small
F 0.15 in
Diameter (in.)
1.2
0.44
7 Thomas is training for a 3.1-mile race by running on a
circular path. He knows that it is 0.75 mile from the
tree in the center of the circular path to the path. How
long is the path? Use 3.14 for π.
F 1.8 mi
4.7 mi
6.7 mi
!
J 7.1 mi
G 0.98 in!
8 Bessie is making an apple pie. The top of the pie pan is
shown below. Approximately how much pie crust will
Bessie need to cover the top of the pie? Use 3.14 for π.
H 1.13in!
J 1.28 in!
5 Sarah wants to cover the rim of her circular pool with a
foam covering. The foam covering is sold in boxes
that will cover 40 feet. How many boxes of foam will
Sarah need to cover the rim of the pool? Use 3.14 for
π.
A 25 in!
B 30 in!
A 2 boxes
C 50 in!
D 71 in!
B 3 boxes
C 5 boxes
D 7 boxes
6 A construction crew is building a circular playground.
The playground is surrounded by a fence that is 47.1
feet long. About how much area will the playground
cover? Use 3.14 for π. Round to the nearest tenth.
9 Several students form a circle by standing next to each
other. Samantha and Aaron are directly across from
each other and are approximately 30 feet apart. If each
student takes up about 4 feet of the circle, how many
students are in the circle? Use 3.14 for π.
Record your answer and fill in the bubbles on your
answer document. Be sure to use the correct place
value.
Record your answer and fill in the bubbles on your
answer document. Be sure to use the correct place
value.
TX102 Course 2 • Expressions, Equations, and Relationships
NAME ____________________________________________ DATE _____________________________ PERIOD _____________
Practice 7.9(B)
SCORE __________
Student Recording Sheet
Fill in the correct answer. For gridded-response questions, write your answers in the boxes on the answer grid and
fill in the bubbles to match your answers.
1
7
2
8
3
9
4
5
6
Course 2 • Expressions, Equations, and Relationships
TX103