Pi’s Early History
Different cultures had different values.
The Ancient Babylonians used 3 1/8 for
their value of pi by taking 3 times the
square of a circles radius which was 3 1/8.
The Egyptians used (16/9)2
The Chinese said pi was 3.
The Hebrews said pi was 3 also, based on
what they learned in the bible.
More of Pi’s History
In Egypt in the 400’s B.C, a mathematician named Euclid
proved that the ratio of the circumference to the diameter
of a circle is always the same.
Archimedes studied in Alexandria. He discovered the value of
pi to be about 22/7 We still use this approximation today.
Archimedes’s method for approximating pi: The
area of the circle is in the areas of the
circumscribed and the inscribed hexagons.
To calculate an approximate value of pi,
measure the diameter and the
circumference of a circle (using a piece of
string perhaps). Divide the circumference
of the circle by the diameter. Keep in mind:
This is an approximation.
Class Activity: #1
Calculate the circumference – C – of the circle above using
one of the following equations:
C=2πr or C=πd
Calculate the area – A – of the circle above using one of the
A=πr2 or A=πd2/ 4
Calculate the volume – V – of the cylinder above using one of
the following equations:
V=πr2h or V=πd2/ 4h
r=radius d=diameter h=height
C = 2πr
C = 2 x 3.14 x 3
C = 18.84 inches
C = πd
C = 3.14 x 6
C = 18.84 inches
A = πr2
A = 3.14 x r x r
A = 3.14 x 3 x 3
A = 28.26 inches
A = πd2/4
A = 3.14 x d x d /4
A = 3.14 x 6 x 6 / 4
A = 28.26 sq. inches
V = πr 2 x h
V= 3.14 x 10 x 10 x 30
V = 9420 cubic inches
The Amazing History of Pi. 23 Apr. 2010. <http://ualr.edu/
The Everlasting Pi. 29 Apr. 2010. <http://abishek.webs.com/