Asked by Callie

Find the surface area of a cone with a radius of 8in. and a height of 7 in.
I forgot the formula how to work this out can somebody help me. Thanks
Answered by Ms. Sue
Google can be a student's best friend. <g>

http://www.google.com/#q=surface+area+of+a+cone
Answered by Anonymous
SA = Lateral Area + Base Area
SA= (pi X radius X slant height) + (pi X r^2)

To find the slant height, use the Pythagorean Theorem.

Let me know if you need more help, it is no trouble at all :)
Answered by Brady
A=πr(r+(√h^2+r^2))

Square root line continues at the top of h^2 through r^2. r is radius and h is height for this problem.

Now substitute numbers for the variables.

A=π8(8+(√7^2+8^2))

Now solve.

The rest I will leave up to you.

I hope this helps! :)
Answered by Callie
I still don't understand how to right it down to show my work. Please right it out for me thanks.
Answered by Callie
The part in the division is what's confusing me,.
Answered by Callie
This is what I get.
3.14*8(8+√49+64
25.12(8+√113
25.12+14.125
=39.245
I know I'm wrong
Answered by Anonymous
Callie, you don't need division I believe.

Multiply pi by the radius and that by the slant height. That counts as the lateral area. Then multiply pi by the radius-squared. Add those together.

Remember the slant height is not the same as the height, so use the Pythagorean Theorem to get this. :)
Hope this helps :)
Answered by Callie
What is the slant height? Or that them your talking about? Can't you just tell me the slant height?
Answered by Anonymous
The slant height would be 10.63014581, or rounded to 10.6 or even 11. Sorry, I thought you knew about the Pythagorean Theorem (a^2 + b^2 = c^2). :(
Anyways, hope this helps ;)
Answered by Ms. Sue
Callie could have used the formula I posted for her.

A=πr(r+h2+r2)
Answered by Anonymous
Very true Ms. Sue :)
Answered by Brady
You don't need to do division. You may be getting confused with the square root sign.

Well, 3.14*8(8+√49+64) is correct. However, you don't need to combine the numbers outside the parentheses just yet. This is because Parentheses comes first in PEMDAS. You must do everything inside the parentheses before you do anything else.

So, you would have 3.14*8(8+√113).

Next you simplify √113.

√113 = 10.630145812734649407999121914929 or 10.6

Now add what's in the parenthesis.

(8 + 10.630145812734649407999121914929) = (18.630145812734649407999121914929) or (18.6)

Now you should have: 3.14*8(18.6).

Next, you Distribute.

8 * 18.6 = 148.8

Now multiply by 3.14.

148.8 * 3.14 = 467.232

Also, Anonymous, I believe you were confusing Callie about the Pythagorean Theorem. Were you meaning about the "r^2 + h^2"? The Pythagorean Theorem is basically r^2 + h^2 in the formula I believe.

For example,

a^2 + b^2 = c^2

r^2 + h^2 = c^2

Basically, you just solve like you have done like the other problems with the Pythagorean Theorem, Callie at this point, but with r^2 + h^2 instead.

I hope this helps! :)
Answered by Brady
It's pretty easy, it's just that you have to remember the order, and formula to use(including the Pythagorean Theorem), Callie. Once you remember those, it can help you with other problems like it.

Also, it took me a while to make the above post, so I am sorry if I have been posting a lot later than what you, Anonymous, and Ms. Sue were talking about. I tried posting as fast as I could, but I had to focus on my own schoolwork.

I'm sorry, and I think I might have killed this thread. :p
Answered by Callie
Lol, and that's ok thanks for the help, Brady:)
Answered by Vaeh <3
thx Brady!
Answered by Vaeh <3
so the answer is 467.232 ???
Answered by Vaeh <3
or is it 527.52?
Answered by XV_TULSA
So whats the answer
Answered by Answer
Whats the answer plzzz
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