Area of Annulus (Ring)

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Show your work for each problem.

1.
What is an annulus?
1. a)A circle with a tangent line
2. b)A full circle
3. c)A semicircle
4. d)A ring-shaped region between two concentric circles
2.
Which formula calculates the area of an annulus with outer radius and inner radius ?
1. a)
2. b)
3. c)
4. d)
3.
An annulus has outer radius cm and inner radius cm. Calculate .
4.
Find the area of an annulus with cm and cm. Give your answer as a multiple of (just the number).
5.
Calculate the area of an annulus with outer radius 6 cm and inner radius 2 cm.
6.
A pipe has outer diameter 8 cm and inner diameter 6 cm. What is the cross-sectional area of the pipe material?
1. a) cm
2. b) cm
3. c) cm
4. d) cm
7.
A circular garden has radius 5 m. A 2 m wide path surrounds it. What is the area of the path? Give answer as a multiple of .
8.
A washer has outer radius 15 mm and inner radius 8 mm. Calculate the area in mm. Round to the nearest whole number.
9.
A pipe has outer diameter 12 cm and wall thickness 2 cm. Find the cross-sectional area of the pipe material.
10.
A dartboard ring has inner radius 50 mm and outer radius 70 mm. Find its area.
11.
If you double both radii of an annulus, by what factor does the area increase?
1. a)4 times
2. b)8 times
3. c)2 times
4. d) times
12.
An annulus has area cm and outer radius 5 cm. What is the inner radius?
13.
A CD has inner recording radius 23 mm and outer recording radius 58 mm. What is the recording area in mm? Round to the nearest integer.
14.
A circular fountain (radius 3 m) is surrounded by a 1.5 m wide walkway, which is bordered by a 0.5 m wide flower bed. Find the total area of walkway plus flower bed.
15.
Two annuli have the same area. The first has and . The second has . Find .