Answer Key
Name:________________________________________________________
Ch. 12 Review Worksheet
Per:__________________
Circumference: C = 𝜋𝑑 or C = 2𝜋𝑟
Area: A = 𝜋𝑟 2
Match the vocabulary terms to the correct definition.
___C___ 1. Radius
a. the distance around the circle
___G___ 2. Diameter
b. approximately 3.14
___A___ 3. Circumference
c. line segment that starts from the center and goes a point on the circle
___F___ 4. Area
d. circles with the same size
___E___ 5. Center of the circle
e. how we name a circle
___B___ 6. Pi
f. the space inside a circle
___D__ 7. Congruent Circles
g. line segment from one edge of the circle to the other side and passes through
the center, cuts the circle in half
8. Find the diameter if a circle has a radius of 3.5 yds.
3.5 + 3.5 = 7 yds
9. Find the radius if a circle has a diameter of 6 miles.
6/2 = 3 miles
10. Find the circumference of a circle if the radius is 9.8 in. C= 9.8 (2) 𝜋 = 61.5 in
11. Find the circumference of a circle is the diameter is 13.1 cm. C= 13.1 𝜋 = 41.13 cm
12. Find the area of a circle is the radius is 2.4 mm. 2.42 𝜋= 18.09 𝑚𝑚2
13. Find the area of a circle if the diameter is 7.8 ft. 7.8/2 3.92 𝜋 = 47.76 𝑓𝑡 2
Determine if the circles are congruent.
14. The radius of circle A is 100 mm. The diameter of circle B is 100 mm. No, radius is half the diameter
15. The diameter of circle A is 20 ft. The radius of circle B is 10 ft.
20= 20 yes
Circle S and Circle U are congruent circles.
1. Name three radii of Circle S. SR ST SU (all labeled as line segments)
2. Name three radii of Circle U. UR UT US ( label as line segments)
3. How are the radii of the two circles related? Explain.
They each have the same radii. Therefore they are the same length and the circles are congruent.
Show the formula you used and all your calculations. If a formula involves π, first give an exact
answer. Then, calculate an approximate answer using 3.14 for π.
7. Compute the circumference of a circle with radius of length 17 inches. 𝜋2𝑟 𝜋2(17) = 106.8 𝑖𝑛2
8. Compute the diameter of a circle with a circumference of 25 feet. 𝜋D
25/ 𝜋 D= 8 ft
9. Compute the area of a circle with radius of length 4.5 centimeters. 𝜋𝑟 2
. 𝜋(4.5)2 63.6 𝑐𝑚2
11. Compute the area of a circle with a circumference of 56π feet. 𝜋𝑟 2
𝜋282
2463𝑓𝑡 2
12. Marlene wants to enclose her circular vegetable garden with fencing to keep rabbits
from eating the vegetables. If the diameter of her garden is 14 feet, how much fencing
will she need to buy? 14𝜋 = 44ft
13. Justin wants to cover the top of a circular swimming pool to keep insects out of the pool.
If the diameter of the pool is 20 feet, what will be the area of the top of the cover?
20/2 r=10 𝜋102 𝜋100 314𝑓𝑡 2
1. A circle is shown.
Identify each of the following in the figure.
a. the center of the circle A
b. a diameter of the circle DB (label as line seg.)
c. three radii of the circle DA AC AB (label as line seg.)
Find the diameter of each circle.
17) area = in²
18) area = yd²
r²
4= r² r=2, D= 4
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19) circumference = yd
r² r=7 D=14
D 162 = D
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20) circumference = yd
D = 30  D
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ft
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ft
c. Compute the circumference of Track #3 using the circumference formula. Let 𝜋 = 3.14.
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ft
3. How much more area does the bigger circle take up compared to the smaller circle on the field?
4²
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8²64or 201
cm²
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A few friends decided one night to make some crop circles. This is
what the sky view looks like.
2. Find the total area that BOTH circles would take up on the field.
3²9
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