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The octahedron is an eight-faced geometric solid that can be thought o

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The octahedron is an eight-faced geometric solid that can be thought o  [#permalink]

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25 Feb 2015, 03:03
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56% (00:57) correct 44% (00:59) wrong based on 93 sessions

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The octahedron is an eight-faced geometric solid that can be thought of as two square-based pyramids with the squares glued together. All eight faces of the octahedron are congruent equilateral triangles. Given that an edge is where the side of one equilateral triangles is attached to the side of another equilateral triangle, how many edges does the octahedron have?

(A) 8
(B) 10
(C) 12
(D) 16
(E) 18

Kudos for a correct solution.

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Re: The octahedron is an eight-faced geometric solid that can be thought o  [#permalink]

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25 Feb 2015, 16:56
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Octahedron has 12 sides answer is c

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Re: The octahedron is an eight-faced geometric solid that can be thought o  [#permalink]

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25 Feb 2015, 22:51
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Bunuel wrote:
The octahedron is an eight-faced geometric solid that can be thought of as two square-based pyramids with the squares glued together. All eight faces of the octahedron are congruent equilateral triangles. Given that an edge is where the side of one equilateral triangles is attached to the side of another equilateral triangle, how many edges does the octahedron have?

(A) 8
(B) 10
(C) 12
(D) 16
(E) 18

Kudos for a correct solution.

ans C... 12..
each pyramid has 4 edges between equilateral triangle and another four are created when two bases are joined..
total4*2+4=12..
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Re: The octahedron is an eight-faced geometric solid that can be thought o  [#permalink]

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02 Mar 2015, 05:32
Bunuel wrote:
The octahedron is an eight-faced geometric solid that can be thought of as two square-based pyramids with the squares glued together. All eight faces of the octahedron are congruent equilateral triangles. Given that an edge is where the side of one equilateral triangles is attached to the side of another equilateral triangle, how many edges does the octahedron have?

(A) 8
(B) 10
(C) 12
(D) 16
(E) 18

Kudos for a correct solution.

MAGOOSH OFFICIAL SOLUTION:

Again, we will use the analogy of Earth’s geography to orient us. (This, in and of itself, is a useful trick to remember.) When we glue together the two square faces, call that the “square equator” of the octagon. That’s a square, so obviously it have four edges. The pyramid above that goes up to a “north pole vertex”, and four edges run down that vertex to the corners of the “square equator,” so that’s four more. Similarly and symmetrically, the upside-down pyramid underneath comes to a point at the “south pole vertex”, with an additional four edges running from that vertex to the “square equator.” That’s four edges on the “square equator”, four more above, four more below, for a total of twelve edges on the octahedron.

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Re: The octahedron is an eight-faced geometric solid that can be thought o  [#permalink]

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02 Mar 2015, 05:32
Bunuel wrote:
The octahedron is an eight-faced geometric solid that can be thought of as two square-based pyramids with the squares glued together. All eight faces of the octahedron are congruent equilateral triangles. Given that an edge is where the side of one equilateral triangles is attached to the side of another equilateral triangle, how many edges does the octahedron have?

(A) 8
(B) 10
(C) 12
(D) 16
(E) 18

Kudos for a correct solution.

Check other 3-D Geometry Questions in our Special Questions Directory.
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Re: The octahedron is an eight-faced geometric solid that can be thought o  [#permalink]

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31 Mar 2016, 14:34
if you can visualize the figure then answer comes out to be 12 in about 15 seconds
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Re: The octahedron is an eight-faced geometric solid that can be thought o  [#permalink]

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04 Oct 2017, 10:28
Hello from the GMAT Club BumpBot!

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Re: The octahedron is an eight-faced geometric solid that can be thought o &nbs [#permalink] 04 Oct 2017, 10:28
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