### 1.1 Earth`sCircumference

```Eratosthenes air-uh-TOS-thuh-neez
2,000 BC
What is the circumference of this apple pie?
(Given: you know about one piece)
90º
---- =
360º
10"
----?"
What is the circumference of this apple pie?
(Given: you know about one piece)
What part of a circle
is 90º?
90º
---- =
360º
10"
----?"
What is the circumference of this apple pie?
(Given: you know about one piece)
¼,
so take 10” times 4.
90º
---- =
360º
10"
----?"
What is the circumference of this apple pie?
(Given: you know about one piece)
10” times 4 = 40”
(or 10 / .25 = 40)
90º
---- =
360º
10"
----40"
What is the
circumference
of this pizza?
45º
---- =
360º
9"
----?"
What is the
circumference
of this pizza?
45º
---- =
360º
9"
----?"
What part of a circle
is 45º ?
What is the
circumference
of this pizza?
45º
---- =
360º
9"
----?"
1/8 ,
so take 9” times 8.
What is the
circumference
of this pizza?
45º
---- =
360º
9"
----72"
so 9” times 8 = 72”
(or 9 / 0.125 = 72)
What is the Circumference
of the
Earth?
Eratosthenes
air-uh-TOS-thuh-neez
2,000 BC
? % of a circle =
7.2º
925 km
---- = ---------360º
? km
H om ew ork: Page 4
What is the Circumference
Eratosthenes
2,000 BC
air-uh-TOS-thuh-neez
7.2º
1/50 = ---- =
360º
925 km
---------? km
(Next, take
925 km
times 50)
What is the Circumference
7.2 / 360 = 0.02
925 / 0.02 = 46,250
7.2º
1/50 = ---- =
360º
925 km
---------46,250 km
```