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Mathematics 15 Online
OpenStudy (anonymous):

Can someone Please show me how to do this Thank you What is the surface area of the prism? A.138 yd2 B.192 yd2 C.264 yd2 D.272 yd2

OpenStudy (anonymous):

OpenStudy (k_lynn):

To find the surface area, you need to find the area of all the sides and then add them up.

OpenStudy (k_lynn):

http://prntscr.com/6zii3y The two triangles outlined in blue are congruent. Find the area of 1, and multiply that area by 2 or just add the area's together.

OpenStudy (anonymous):

the book shows to uses these formulas and when you plug everything in it does not match the answers

OpenStudy (k_lynn):

what are the formulas they give you?

OpenStudy (anonymous):

SA=2B+PH B=1/2BH

OpenStudy (anonymous):

and then it shows to get the perimeter

OpenStudy (k_lynn):

Hmm. I think those formulas make it a little confusing. Do you mind if I show you a simpler way to remember how to find Surface area?

OpenStudy (anonymous):

please do thank you

OpenStudy (k_lynn):

Ok. When I need to find the surface area, you just need to remember that you have to find the area of the surface. Like, you can see different shapes that make up the prism given. There's the two triangles and a few rectangles. What you have to do to find the surface area. Is find the area of all those little shapes. Then once you found the area of those shapes, add them together. Let's start with the rectangles. I'll outline the one we'll do first in blue. http://prntscr.com/6zikur The area formula of a rectangle is \[Length \times Width\]Those are the two numbers given. All you need to do to find the area is multiply them together. What do you get when you do that? \[10\times9\]

OpenStudy (anonymous):

so you take 10x9=90 like that

OpenStudy (k_lynn):

Yep. Now you know one area. Let's find another area. http://prntscr.com/6zimqe I outlined the rectangle in blue again.

OpenStudy (anonymous):

then you find the 2 areas of the triangle which is 24 then add everything together 90+24+24=138

OpenStudy (k_lynn):

You have the right idea to add. But the area of the triangle isn't correct. We have to find the area's of the other rectangles first.

OpenStudy (anonymous):

oh ok

OpenStudy (k_lynn):

http://prntscr.com/6ziny9 We have to find those areas first. Do you want to do the one outlined in red first or the one in blue?

OpenStudy (anonymous):

blue

OpenStudy (k_lynn):

ok. http://prntscr.com/6ziom2 We need to multiply \[6\times9\]

OpenStudy (anonymous):

54

OpenStudy (anonymous):

would the red be 8x9

OpenStudy (k_lynn):

Right, what do you get when you multiply that?

OpenStudy (anonymous):

72

OpenStudy (anonymous):

so you add everything together 264 24+24+90+54+72

OpenStudy (k_lynn):

Yep. We have 90, 54, and 72. We can find the triangles now. Triangles have a different area formula. It's \[ \frac{ l \times h}{ 2 }\]

OpenStudy (k_lynn):

Yep, 264 is the right answer. :)

OpenStudy (anonymous):

so you break every shape down and then add them all together,your way is way easier then what there trying to show Thank you so much

OpenStudy (k_lynn):

:) You're welcome.

OpenStudy (k_lynn):

I can try. You'll do the same thing. http://prntscr.com/6zisde There's a rectangle hiding beside the red and yellow colors.

OpenStudy (k_lynn):

There's a million ways you could try to break that shape down, but that's how I seen it.

OpenStudy (anonymous):

ok so if we do blue it woud be 4x15

OpenStudy (k_lynn):

Yep.

OpenStudy (anonymous):

red would be 9x15

OpenStudy (k_lynn):

Right.

OpenStudy (anonymous):

yellow would be 9x4

OpenStudy (k_lynn):

Yep. Keep going. :D

OpenStudy (anonymous):

green would be 6x6

OpenStudy (k_lynn):

Yes.

OpenStudy (anonymous):

peach would be the same 6x6

OpenStudy (k_lynn):

You have the first 6 right. But look again. http://prntscr.com/6ziv9u

OpenStudy (anonymous):

or would it be 4x6

OpenStudy (k_lynn):

Yep. 6x4

OpenStudy (anonymous):

now do we add it all together?

OpenStudy (k_lynn):

There's also the one we can't see and the bottom of the shape. Since the shape is 3d, some of the sides have backs.

OpenStudy (anonymous):

ok we would just add the peach # twice same with the Green #?

OpenStudy (k_lynn):

http://prntscr.com/6zivzl There's shapes under the red. Behind the blue and beside the red and yellow. Add green twice, but peach doesn't need to be added 2 times. Red does. Green and red are added twice.

OpenStudy (k_lynn):

http://prntscr.com/6ziwuo There's that shape. and we need the bottom, too. http://prntscr.com/6zix3f

OpenStudy (k_lynn):

After that, you'll be done.

OpenStudy (anonymous):

ok let me add them all together and see what I get

OpenStudy (k_lynn):

Right.

OpenStudy (anonymous):

Hmm my answers doesn't equal the answers to pick from let me break it down and maybe you can see my mistake

OpenStudy (k_lynn):

So: Blue-15x4 red-15x9 red-15x9 green-6x6 green-6x6 peach-6x4 yellow-6x4 side-9x4 bottom-15x4

OpenStudy (k_lynn):

oops. I think I forgot another shape :/ http://prntscr.com/6ziyuh

OpenStudy (anonymous):

60+135+135+36+36+24+24+36+60=546

OpenStudy (anonymous):

would that one be 6x4

OpenStudy (k_lynn):

yep. 6x4. I think that's where we went wrong.

OpenStudy (anonymous):

hmm the answers still dont match haha sorry this is taking so long

OpenStudy (k_lynn):

what are your options?

OpenStudy (anonymous):

900 582 399 291

OpenStudy (k_lynn):

huh. @confluxepic do you know where we went wrong?

OpenStudy (anonymous):

cause I get 570 adding it all together

OpenStudy (k_lynn):

I get the same answer. I don't think we missed any shapes, but I'm not sure.

OpenStudy (confluxepic):

It may take me a while since I will be reading every post in this question. @k_lynn

OpenStudy (k_lynn):

ok. do you mind @kenzie707 ?

OpenStudy (anonymous):

no not at all

OpenStudy (k_lynn):

okie doke.

OpenStudy (confluxepic):

For the big rectangle at the side: \(\large\ 8\times 9=72\) For the two triangles: The are of a triangle is \(\large\frac{1}{2}6\times 8=24\) Double that to get the area of both the triangles which is 48. \(\large(\frac{1}{2}6\times 8)(2)=48\) For the bottom rectangle: \(\large\ 9\times 6=54\) For the slanted rectangle at the top: \(\large\ 10\times 9=90\) Now add them all up. \(\large\ 72+48+54+90=264\)

OpenStudy (anonymous):

opps not that one this one

OpenStudy (confluxepic):

Oh wait. I did the wrong question.

OpenStudy (confluxepic):

Do you have to find the volume or the surface area?

OpenStudy (anonymous):

surface area

OpenStudy (confluxepic):

Ok.

OpenStudy (confluxepic):

Did you forget to add the surface are of the hidden part?

OpenStudy (k_lynn):

http://prntscr.com/6zj6b3 That part?

OpenStudy (confluxepic):

http://prntscr.com/6zj6gc

OpenStudy (k_lynn):

I remember seeing that and start to type that we needed to remember that one, but I forget if I did mention it. SO no, I don't think we added that.

OpenStudy (confluxepic):

Then that's probably the mistake.

OpenStudy (k_lynn):

That would have been where we messed up @kenzie707 we still have to add that part.

OpenStudy (k_lynn):

Thanks @confluxepic

OpenStudy (anonymous):

Thanks Confluxepic

OpenStudy (confluxepic):

No problem. :)

OpenStudy (k_lynn):

\(\color{blue}{\text{Originally Posted by}}\) @k_lynn So: Blue-15x4 red-15x9 red-15x9 green-6x6 green-6x6 peach-6x4 yellow-6x4 side-9x4 bottom-15x4 \(\color{blue}{\text{End of Quote}}\) other side:

OpenStudy (k_lynn):

What are we going to multiply @kenzie707 to get the invisi-side

OpenStudy (anonymous):

6x4?

OpenStudy (k_lynn):

yes.

OpenStudy (anonymous):

what do you get because my answer still doesnt match

OpenStudy (k_lynn):

My answer doesn't match either.

OpenStudy (anonymous):

weird I will ask the teacher

OpenStudy (k_lynn):

okie doke.

OpenStudy (anonymous):

Thank you for all your help

OpenStudy (k_lynn):

Sure, no problem. Glad to help you.

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