richardlong369
Find surface Area & Volume of the regular pentagonal pyramid
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richardlong369
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Mertsj
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First find the area of the base. The formula is 1/2(perimeter)(apothem)
Mertsj
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Find that and tell me what you get.
richardlong369
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177.975
Mertsj
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Yes. That's what I got.
Mertsj
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Not we have to find the area of one of those triangles and multiply by 5. I'll draw a picture. We know the base is 10.17 and the slant height is the height of the triangle.
Mertsj
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|dw:1339278986157:dw|
Mertsj
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Find the area of that triangle and multiply it by 5
richardlong369
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127.125
Mertsj
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Is that one triangle or all 5?
richardlong369
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one
richardlong369
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5 would be 635.625
Mertsj
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Now add the area of the base that we calculated earlier. That should be the total surface area.
richardlong369
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SA = 762.75 ?
Mertsj
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What is the area of the base?
richardlong369
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50.85
richardlong369
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i mean 635.625
Mertsj
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What is the area of the 5 triangles?
richardlong369
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635.625
Mertsj
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First find the area of the base. The formula is 1/2(perimeter)(apothem)12 minutes ago
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Mertsj
0Find that and tell me what you get.11 minutes ago
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richardlong369
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0177.975
Mertsj
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If you look back through the posts you will find the area of the base and the area of the 5 triangles. Add them together to get the total area.
richardlong369
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813.6
Mertsj
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yes. That is the surface area.
Mertsj
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Now the volume. Fortunately we are partly done with the volume because we already know the area of the base.
Mertsj
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So find that number. The area of the base.
To find the volume multiply these 3 numbers: 1/3, the area of the base, and the height of the pyramid which is shown in the picture to be what?
richardlong369
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i got 13361.486
Mertsj
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What is the height?
richardlong369
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25
Mertsj
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That's the slant height. Look at the picture.
richardlong369
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24
richardlong369
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its 24
Mertsj
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The slant height is the height of the triangles that make the pyramid.
Mertsj
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Yes. 1/3(24)=8 so multiply 8 times the area of the base. What do you get?
richardlong369
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1423.8
Mertsj
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That's what I got as well. That would be m^3
richardlong369
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thankyou
Mertsj
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yw