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Encourage students to work in pairs on the proof sorting exercise.
Three Consecutive Odd Numbers
Age 11 to 16
Challenge Level 
Why do this problem?
This problem, along with the rest of the problems in the Proof for All (st)ages feature, provides an excellent context for observing, conjecturing and thinking about proof, and for appreciating the power of algebra.
Possible approach
These printable cards for sorting may be useful:
Three Consecutive Odd Numbers Proof Sort
Possible support
Encourage students to work in pairs on the proof sorting exercise.
Before embarking on this problem, students could take a look at Sieve of Eratosthenes and I Like to Prove It! (which contains a collection of more accessible problems that also challenge students to develop convincing arguments).
Possible extension
Students could be encouraged to work on the rest of the problems in the Proof for All (st)ages feature.
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