Stage: 4 Challenge Level: 
Suppose 20 fish are re-caught - that's 20 of the 40 caught first - what would be a good guess for the whole lake fish population in this case?
Short problems. Forces. engineering. Mathematical reasoning & proof. physics. Fractions. Sampling and hypothesis tests. biology. Rigid Bodies. Modulus arithmetic.
Published July 2008,August 2008.
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