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## sammy12 3 years ago A solid candy jawbreaker is cut in half. If its diameter is 4 cm, what is the surface area of a half piece? please show me the steps.

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1. beth1127

|dw:1328844308091:dw|

2. sammy12

i am getting 8 pi .is it right

3. Tonik

i think it should be 48pi

4. Tonik

oh hell, no.... i thought radius was 4, not diameter... sec

5. sammy12

answer is 12 pi.I don't know how

6. funinabox

2A = 4pi*r^2 2A = 4pi*(2)^2 2A = 16pi A = 8pi I set it equal to 2A because we want half the surface area, I found the full SA then divided by 2.

7. sammy12

i am getting 8 pi

8. Tonik

the surface area on the outside is 8pi, you're correct, but you need to add the surface are where the cut was made (basically the area of a circle radius 4

9. Tonik

ugh, radius 2

10. Tonik

so its 12pi

11. sammy12

please can you explain

12. funinabox

Ahhh yes I forgot about the inside cut. I assumed a hollow sphere. :O stupid mee

13. Xishem

It's the surface area of half a sphere plus the surface area of the circle... $\frac{4πr^2}{2}+\pi r^2=2 \pi r^2+\pi r ^2=3 \pi r^2= 3 \pi (2cm)^2=12 \pi\ cm$

14. Xishem

*$12\pi\ cm^2$

15. sammy12

Thanks

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