Magic Octahedron
Age 11 to 14
ShortChallenge Level 
The diagram show the net of a regular octahedron.
In a magic octahedron, the four numbers on the faces that meet at a vertex add up to make the same total for every vertex. If the letters $F, G, H, J$ and $K$ are replaced with the numbers $2$, $4$, $6$, $8$, and some other number, in some order, to make a magic octahedron, what is the value of $G + J$?
If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.
This problem is taken from the UKMT Mathematical Challenges.
You can find more short problems, arranged by curriculum topic, in our short problems collection.
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