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'Three Ball Line Up' printed from http://nrich.maths.org/
If you are not using the interactivity, perhaps you could find three differently coloured balls, counters or cubes to try out some ideas. Or you could just use coloured pencils and draw three spots.
If red landed in the middle, how could the blue and green fall?
Where else could red land if it wasn't in the middle? Can you use this idea to find all the ways?