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

Question

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.

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

Kudos for a correct  solution .

ynaikavde · Answer

Octahedron has 12 sides answer is c

https://australianmuseum.net.au/Uploads/Images/10715/7_crystal_systems-cubic-oct.jpg

chetan2u · Answer

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..

Bunuel · Answer

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.

Answer = C.

Bunuel · Answer

Check other  3-D Geometry Questions  in our  Special Questions Directory .

rhine29388 · Answer

if you can visualize the figure then answer comes out to be 12 in about 15 seconds
answer - C

chrtpmdr · Answer

How do you see 12 edges there?!

bumpbot · Answer

Automated notice from GMAT Club BumpBot: 

A member just gave Kudos to this thread, showing it’s still useful. I’ve bumped it to the top so more people can benefit. Feel free to add your own questions or solutions.

 This post was generated automatically.

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

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards

GMAT Problem Solving (PS) Questions

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

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards