Perimeter and circles
4,000
years ago (2,000 B.C.) the Babylonians, Sumerians and Chaldeans knew the
existence of 
and had estimated
it to be roughly equal to 3.
For simplicity, we will use
3.142 to equal .
r.
Where r is the radius of the circle and
is given as 3.142.Consider the animation on the right.
A circle of radius ten metres is expected to have a circumference (perimeter) of 62.84 m.
Consider the animation on the right.
Three quarters of a circle of radius ten metres is expected to have a circumference (perimeter) of 47.13 m.
Consider the animation on the right.
Half a circle of radius ten metres is expected to have a circumference (perimeter) of 31.42 m.
