Problem 23 · 2019 Math Kangaroo
Stretch
Spatial & Visual Reasoning
net-folding
The diagram shows the net of an octahedron. Which edge meets the edge labelled with x if the net is folded up to form an octahedron?
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Answer: E — 5
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Hint 1 of 3
Fold the strip of eight triangles into the octahedron and track where edge x lands.
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Hint 2 of 3
Two open edges of the net get glued together — find x's partner.
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Hint 3 of 3
Number the boundary edges and pair the ones that join when folded.
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Approach: fold the net and match the glued edges
- Folding the eight-triangle net brings its two open boundary edges together.
- Following the fold, the edge marked x is glued to the edge labelled 5.
- So edge x meets edge 5.
Mark:
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