Math
posted by Hannie on .
How do you calculate the perimeter of a half circle?

perimeter of circle = pi*diameter OR
2*pi*radius.
http://math.about.com/od/formulas/ss/areaperimeter_5.htm 
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.

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.

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. :)