Geometry

Question Analysis  
This question uses classroom activity data to test non-mutually exclusive event probability.
The focus is applying the union formula to overlapping game players.  

Key Concept Explanation  
For non - mutually exclusive events A and B, the probability of A or B is given by P(A ∪ B) = P(A) + P(B) - P(A ∩ B).
Events A (chess) and B (checkers) overlap; the formula subtracts the both-players count to avoid double-counting.  

Step-by-Step Solution  
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