Stage: 4 Challenge Level: 
This problem deliberately has small numbers (four coins or three dice) but the visualisation challenge is significant and makes a good preliminary to post-16 probability work.
Combinatorics. Real world. Experimental probability. Theoretical probability. Tree diagrams. Quadratic equations. Mathematical modelling. Equally likely outcomes. Conditional probability. Combining probabilities.
Published November 2005,December 2005.
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