Circles

FormulasRadius= diameterDiameter = 2 · radius

Circumference =  · diameterArea =  · radius2

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1.The radius of a circle is 5 inches. What is the

a)diameterb) circumference c) area

2.The diameter of a circular rug is 6.8 feet.

a) What is the radius?

b)Circumference Formula?In terms of Nearest Tenth

c) Area Formula?In terms of Nearest Tenth

3.If a circle has an area of 144, what is the radius and diameter? Also, find the circumference.

4.If a circle has a circumference of 42, what is the diameter and radius? Also, find the area.

5.Find the missing measures. Show your work

Radius
Nearest Whole # / Diameter
Nearest Whole # / Circumference
  • In terms of 
  • Nearest Tenth
/ Area
  • In terms of 
  • Nearest Tenth

a. / r = 7
r2 = / d = / C = d / A = r2
b. / r =
r2 = / d = 22 / C = d / A = r2
c. / r =
r2 = / d = / C = d
C = 50.3 / A = r2
d. / r =
r2 = / d = / C = d / A = r2
A = 36
e. / r =
r2 = / d = / C = d
C = 20 / A = r2
f. / r =
r2 = / d = / C = d / A = r2
A = 78.6
g. / r =
r2 = / d = / C = d / A = r2
A = 49
h. / r =
r2 = / d = / C = d
C = 18 / A = r2

6.If a circle has a circumference of 137in., what is the diameter to the nearest whole number?

What is the area in terms of ?

7.If a circle has an area of 254ft2, what is the radius to the nearest whole number?

What is the circumference in terms of ?

8.A paper plate has a diameter of 10 inches. What is the area of the plate?

Write your answer in terms of  and to the nearest tenth.

Find the plate’s circumference to the nearest hundredth.

9.A circular light fixture has a radius of 20 centimeters. What is the circumference of the light fixture?

Write your answer in terms of  and to the nearest tenth.

Find the area of the light fixture in terms of  and to the nearest tenth.

10.11.

GK = 6MN = 8

Radius = ______Diameter = ______Radius = ______Diameter = ______

In Terms of πIn Terms of π

Area = ______Circumference = ______Area = ______Circumference = ______

To the nearest tenthTo the nearest tenth

Area = ______Circumference = ______Area = ______Circumference = ______

12.A circular garden has an area of 81π square yards.

a)What is the circumference of the garden (in terms of)?

b)What happens to the area of the garden if the circumference (found in Part A) is doubled?

(Leave all calculations in terms of )

13.A small silver dollar pancake served at restaurant has a circumference of 4π inches. A regular pancake has acircumference of 8π inches. Is the area of the regular pancake twice the area of the silver dollar pancake? Prove why or why not.

Circumference HW

Find the radius or diameter of each circle with the given dimensions.

1. d= 18 in. 2.d= 29 m 3. r = 21 ft 4.r = 13 mm

Find the circumference of each circle. State your answer in terms of and to the nearest tenth.

5. 6.7.

8. PLANTS The world’s largest flower, the Giant Rafflesia, is 91 centimeters in diameter. Use a calculator to find the circumference of a Giant Rafflesia to the nearest tenth.

9. GEOLOGY Ubehebe Crater in Death Valley has a diameter of a little more than mile. If Latisha walks around its rim at a rate of 2 miles per hour, about how long will it take her to walk all the way around the crater? Find your answer to the nearest tenth.

For each of the following circumference, find the diameter and the radius.

10. C = 32π11.C = 12π12.C = 75.413.C = 34.6

Area of Circles HW

Find the area of each circle. Round to the nearest tenth and also state your answer in terms of .

1. 2.3.

4.5.6.

7. SPOTLIGHT A spotlight can be adjusted to effectively light a circular area of up to 6 meters in diameter. To the nearest tenth, what is the maximum area that can be effectively lit by the spotlight?

For each of the following area, find the radius and the diameter.

8.A = 49π9.A = 400π10.A = 28.311.A = 380.5

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