Page 39 - SPARK OF MATH book 6

To find the diameter use this formula:
Diameter= 2xradius or

Example: a bicycle wheel has a radius of 311

millimeters, what is the diameter of the wheel?
d= 2r= 2 (311 mm) The diameter of the bicycle

wheel is 622 mm.

Find the radius and diameter.

radius= radius= radius= radius=
diameter= diameter= diameter= diameter=

Because a circle is round in shape, we do not call the distance around
the outside, the perimeter. Instead, we call it the circumference.
To calculate the circumference use the formula:

Circumference = 2x π x r ( )
The symbol π is called Pi.
Note: Because 2 x r is the same as the diameter,

you also can write the formula as C= π x d. Pi is the ratio of a circle's
circumference to its diameter.

Example:

2×3.14×5 cm
cm

Find the circumference of each circle below.

39