



Tools  Math 'Convincing and Proving' Critiquing 'Proofs' Tasks, Set #3
Always, Sometimes or Never True: Set #1 (solutions)  Set #2 (solutions) Critiquing 'Proofs': Set #3 (solutions)  Set #4 (solutions)
Malcolm Swan
Jim Ridgway
1. Consecutive Addends Here are three attempts at proving the following statement: When you add add three consecutive numbers, your answer is always a multiple of three. Look carefully at each attempt. Which is the best 'proof'? Explain your reasoning as fully as possible.
The best proof is attempt number ..........
Here are three attempts at proving the following statement: If you have two rectangles, the one with the greater perimeter will have the greater area. Which is the best 'proof'? Explain your reasoning as fully as possible.
The best proof is attempt number ..........
A student is playing a coin turning game. She starts with three heads showing and then turns them over, two at a time.
After a while she makes the statement: Here are three attempts to prove this. Look carefully at each attempt. Which is the best 'proof'? Explain your reasoning as fully as possible.
The best proof is attempt number ..........
Critiquing 'Proofs': Set #3 (solutions)  Set #4 (solutions)

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