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'Olympic Magic' printed from https://nrich.maths.org/
The four overlapping regions could be edges in a graph and the
remaining regions vertices. Each vertex and each edge has a unique
number assigned to it. This is a problem on vertex magic graphs! A
graph is vertex magic if, for each vertex, we get the same magic
sum when we add the number at that vertex to the numbers on all the
edges joined to that vertex.
What is the grand total of the sums at the 5 vertices? The numbers
on the edges are counted twice so add this to the total of the
numbers 1 to 8. What does this tell you about the total of the
numbers on the edges (that is in the overlapping regions)? This
gives you information about the possible values for the magic
sum.
Be systematic and you?ll be able to check all the
possibilities. What pairs of numbers can you use in the outer
circles? What numbers can you then use in the overlapping regions
(the edges of the graph).
There are several solutions. How will you know when you have found
them all?