Circle Similarity

All circles are similar.

• True

• False

The radius of one circle is 9mm and the radius of a second circle is 21mm. What is the ratio of their circumferences in simplest form?

• 9:21

• 1:3

• 3:7

• 9:49

The circumference of Circle A is 24π feet.

The circumference of Circle B is 4π feet.

What is the ratio of their radii in simplest form?

• 24:4

• 48:8

• 1:6

• 6:1

Circle A has a diameter of 25m. Circle B has a diameter of x.

If Circle A has and area of 78.5 square meters and

Circle B has an area of 706.5 square meters, what is the diameter of Circle B?

(hint: draw a picture)

• 25 meters

• 9 meters

• 225 meters

• 125 meters

What is the translation vector for Circle B to Circle A?

• (x, y) →(x + 8, y - 4)

• (x, y) →(x - 4, y + 8 )

• (x, y) →(x - 8, y + 4)

• (x, y) →(x + 4, y - 8)

What is the dilation scale factor for mapping circle B onto circle A?

• 9/16

• 4/3

• 3/4

• 1

Circles X and Y have a similarity ratio of 1/2. Which of the following could NOT be true about the circles?

• Circle X has a radius of 5 while Circle Y has a radius of 10.

• Circle X has a circumference of 15π and Circle Y has a circumference of 30π.

• Circle X has a radius of 6 while Circle Y has a radius of 12.

• Circle X has a circumference of 60π while Circle Y has a circumference of 20π.

If the scale factor between two arcs is 5/6, then the ratio of areas is...

• 5:6

• 10:12

• 25:36

• 125:216

If the ratio of areas is 9:121, then the scale factor of the arc lengths could be...

(select all that apply)

• 3/11

• 9/121

• 11/3

• 121/9

The radius of one circle is 9mm and the radius of a second circle is 21mm. What is the ratio of their areas in simplest form?

• 9:21

• 1:3

• 3:7

• 9:49