## crystal1 3 years ago Dana plans to cover this model of a half moon completely with silver foil. How many square centimeters of silver foil would Dana need to cover the model completely? 402.2 536.2 603.4 150.8

1. crystal1

2. trackzz

Dude, this is a homework help site, do not ask for emails :P

3. crystal1

its not and ur a player

4. crystal1

true @trackzz

5. campbell_st

well the surface area of a hemisphere is $SA = \frac{1}{2}(4pir^2) + \pi r^2$ and you have a radius of 8 cm just substitute and solve.

6. crystal1

i dont know how to do that

7. crystal1

cause i just see leters

8. crystal1

@campbell_st

9. campbell_st

ok... do you have a calculator ?

10. crystal1

yesss

11. campbell_st

ok you need to type in $0.5 \times 4 \times \pi \times 8^2 + \pi \times 8^2$ that will give the answer to covering the hemisphere in foil..

12. trackzz

Alrii so basically what campbell has show you is the surface are of a sphere. Any problem in which they ask for something that wraps around a specific shape involves surface are. The surface area of a sphere is: 4 pi r^2 Where r is the radius of the sphere.

13. crystal1

what is p 12.18 or 12.14

14. trackzz

If you're familiar with the button pi, it is the value of 3.14. Now for this particular question, it is a hemisphere. So half the surface are of the sphere. 1/2*(4pi r^2) = SA

15. crystal1

thnks

16. trackzz

@crystal1 what are you talking about>

17. trackzz

you said:" what is p 12.18 or 12.14" what do you mean?

18. crystal1

19. trackzz

20. crystal1

wait

21. crystal1

22. campbell_st

nope... thats a long way from being correct

23. campbell_st

did you type in the equation I gave you as its written...?

24. trackzz

Shall we break it down Campbell? I think it's the BEDMAS

25. trackzz

Alright crystal, I want you to do r^2 first. Find the value of the radius squared.

26. crystal1

yes i did @campbell_st

27. campbell_st

and tracks... I think you possible solution is missing the circular base... as the question talks about competely covering... it

28. crystal1

you guys lost me now im confuse

29. campbell_st

ok... lets to it in little bits can you calculate $0.5 \times 4 \times \pi \times 8^2$

30. trackzz

Ok my bad, alrii yeah you're right. I'll leave this to Campbell. Dont wanna confuse you,

31. campbell_st

@crystal1 did you get an answer for the new calculation..?

32. crystal1

b

33. campbell_st

what was the number..?

34. crystal1

i dont reaally know im sorry im dumb i dont know how to start this thats why i need help

35. trackzz

You're not dumb. Tell yourself you're smart. You'll get the answer. Crystal, you got this. Wake up, look at what campbell wrote for you.

36. crystal1

37. trackzz

you're not finished yet. Add the pi r^2 to what you got to get the answer

38. campbell_st

nope thats only the 1st part of the problem the curved surface has an area of 402.2 cm^2 now you need to find the area of the circular base... $\pi \times 8^2$

39. campbell_st

you need to calculate this number...

40. campbell_st

then the final answer will be $402.2 + \pi \times 8^2 =$

41. crystal1

6485.44

42. campbell_st

wow... nope not it lets make it easier what is $\pi \times 8^2 =$

43. crystal1

75.36

44. campbell_st

nope still not right... $\pi \times 8^2 = 201.1$

45. crystal1

how do you get thaat i tough that 8x2 its = 24

46. campbell_st

do you know how to square a number...

47. crystal1

no

48. campbell_st

ok... then perhaps you need to ask you teacher... how to do the problem is you don't know the basics...

49. crystal1

thnks you @campbell_st