Circles and Similarity

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

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

• 5:6

• 10:12

• 25:36

• 125:216

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

• 9

• 3

• 1/3

What is the part of the circle highlighted in red called?

• semi-circle arc

• major arc

• minor arc

• sector

In the equation (x+2)²+(y-3)²=4, the radius of the circle is...

• 4

• 2

• 3

• 16

An angle whose vertex is the center of a circle

• central angle

• inscribed angle

• minor arc

• major arc

Write the equation of a circle with center (7, 0) with radius 3.

• (x - 7)² + y² = 9

• x² + (y -7)² = 9

• (x - 7)² + y² = 3

• x² + (y -7)² = 3