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Coloured Edges

Age 11 to 14 Challenge Level:

Laura Turner and Laura Malarkey from the Mount School have explained how they worked out the answer to this problem:

n is equal to the number of tiles along one side.

We can calculate the number of edges in two different ways:

Method 1 - In total there are $n²$ tiles on $4n²$ edges.

Method 2 - There are a total of $2n$ green edges which implies there are a total of $20n$ edges of all colours.


$20n = 4n²$

$5n = n²$ (divide by $4$)

$5 = n$ (divide by $n$)

So there are $25$ tiles in the set.