Name: Date: Period:

Circles: Relating Radius, Diameter, and Circumference-Notes

Highlight the radius.If the radius is 4ÿ whatis the diameter?Write an equation, interms of radiusr to findthe diameter.

It takes two strings the length The following is a picture ofof my radius to make the the 2 radii (radius plural) ordiameter, the length of the diameter.

Radius ApproximateCircumference

Radius = 3

Radius =

Diameter

Diameter=

Diameter= 14

I took the diameter and

wrapped it around mycircle, about how manytimes?The extra is the value afterthe decimal: .14 .....

Write an equation using thediameter to find thecircumference.

Write an equation using theradius to find thecircumference.

What is theCircumference?

Highlight the diameter.If the diameter is t 2, what isthe radius?Write an equation in terms ofdiameter to find the radius.

Radius Diameter Approximate What is theCircumference Circumference?

Radius = Diameter= 8

Radius = 52

t b

Radius =

Radius = 5

Radius = Diameter= 30

Diameter=

Diameter= 42

Diameter=

/----.,t )

Circles: Relating Radius, Diameter, and Circumference-Homework

Use this circte to answer questions 1mid 2.

3ÿ What is the diameter oftheouter circle?

.

What is tile ':approximatecircumference of this circle7

A. 5 mm

B. 10 mm

C. 15 mm

D. 20 ran1

9

A. 2.5 mm

B. 5 mm

C. 7.5 mm

D. 9 mm

What is the radius of thiscircle?

A, 2fl

B. 3ft

C. 8ft

D. 5fi

What is the approximatemrcumferenc-' - - - " e of a circle wiffÿ a

diameter of 3 yards?

A. 6 yds

B. 8 yds

C. 7 yds

D. 9 yds

5. 7.

The radius of a circle is l 0inches. How does a diameter of

the circle compare to the

radius/

The PTA painted a giant cu'clcon flÿe playground. *i]ÿediameter of the circle was 28feet. What was the radius of thecircle?

aÿ The diameter is 2 timesthe radius.

B, The diameter is-1 the2

radius,

A. 56 tt

B, 7ft

C, I4ft

D. 2!1!

Dÿ The diameter is 3 timesthe radius.

o

The radius of a circle is 9centimeters. What is theapproximate measure of thecircle's circumference?

A. 18 cm

B. 54 cm

C. 14 em

D. 27 cm

radius.

C. qÿe diameter is 1 the3

.

The circumference of a lamp is 36 inches.

Which of the following could possibly bethe diameter of the lamp?

A. 12 inches

B. 24 inches

C. 36 inches

D. 48 inches