crystal1
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
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crystal1
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trackzz
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Dude, this is a homework help site, do not ask for emails :P
crystal1
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its not and ur a player
crystal1
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true @trackzz
campbell_st
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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.
crystal1
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i dont know how to do that
crystal1
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cause i just see leters
crystal1
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@campbell_st
campbell_st
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ok... do you have a calculator ?
crystal1
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yesss
campbell_st
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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..
trackzz
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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.
crystal1
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what is p 12.18 or 12.14
trackzz
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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
crystal1
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thnks
trackzz
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@crystal1 what are you talking about>
trackzz
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you said:" what is p 12.18 or 12.14"
what do you mean?
crystal1
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my bad sorry
trackzz
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so you got the answer?
crystal1
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wait
crystal1
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my answer is 5048.1152
campbell_st
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nope... thats a long way from being correct
campbell_st
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did you type in the equation I gave you as its written...?
trackzz
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Shall we break it down Campbell?
I think it's the BEDMAS
trackzz
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Alright crystal, I want you to do r^2 first. Find the value of the radius squared.
crystal1
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yes i did @campbell_st
campbell_st
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and tracks... I think you possible solution is missing the circular base... as the question talks about competely covering... it
crystal1
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you guys lost me now im confuse
campbell_st
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ok... lets to it in little bits can you calculate
\[0.5 \times 4 \times \pi \times 8^2\]
trackzz
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Ok my bad, alrii yeah you're right. I'll leave this to Campbell. Dont wanna confuse you,
campbell_st
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@crystal1 did you get an answer for the new calculation..?
crystal1
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b
campbell_st
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what was the number..?
crystal1
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i dont reaally know im sorry im dumb i dont know how to start this thats why i need help
trackzz
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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.
crystal1
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the answer is a
trackzz
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you're not finished yet. Add the pi r^2 to what you got to get the answer
campbell_st
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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...
\[\pi \times 8^2\]
campbell_st
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you need to calculate this number...
campbell_st
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then the final answer will be
\[402.2 + \pi \times 8^2 = \]
crystal1
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6485.44
campbell_st
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wow... nope not it
lets make it easier
what is
\[\pi \times 8^2 =\]
crystal1
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75.36
campbell_st
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nope still not right...
\[\pi \times 8^2 = 201.1\]
crystal1
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how do you get thaat i tough that 8x2 its = 24
campbell_st
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do you know how to square a number...
crystal1
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no
campbell_st
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ok... then perhaps you need to ask you teacher... how to do the problem is you don't know the basics...
crystal1
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thnks you @campbell_st