Stage: 3 Challenge Level: 
Six points are arranged in space so that no three are collinear.
How many line segments can be formed by joining the points in
pairs?
If all the line segments are coloured either red or green prove
that there is a triangle all of whose sides are of the same
colour.
Generalising. Visualising. Patterned numbers. Counting. Mathematical reasoning & proof. Number theory. Pythagoras' theorem. Number - generally. Creating expressions/formulae. Combinatorics.
Published May 1998.
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