Posted by **Hannie** on Tuesday, July 22, 2008 at 12:06am.

How do you calculate the perimeter of a half circle?

- Math -
**DrBob222**, Tuesday, July 22, 2008 at 12:11am
perimeter of circle = pi*diameter OR

2*pi*radius.

http://math.about.com/od/formulas/ss/areaperimeter_5.htm

- Math -
**Hannie**, Tuesday, July 22, 2008 at 12:16am
The question says that the diameter is 8 cm, and then it asks to fnd the perimeter. I found the answer using your formula but when I checked the back of the book, it said the answer was 20.56 cm, not 25.12 cm.

- Math -
**DrBob222**, Tuesday, July 22, 2008 at 12:44am
My calculator says 3.14159*8.00 = 25.13274 which rounds to 25.13 cm. The answer in the book must be wrong. Even if we rounded the pi number to 3.0 that x 8 = 24 cm.

- Math -
**Hannie**, Tuesday, July 22, 2008 at 12:51am
Okay. Thank you very much. I had a feeling that the answer at the back was wrong, I tried many solutions, and it didn't work. So you're probably right. :)

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