I use challenge 1 and 2 frequently but instead of using challenge 3 where I ask students to explain why the wrong answers are wrong, I ask them to explain why the correct answers are correct.
I find this focuses them on the mathematical conceptual understanding and also unearths reasons such as "I guessed." It's important to check how students get their answers. I have found challenge 2 quite useful in getting students to actually work out an answer rather than making a quick guess or a calculated guess where they arrive at an answer by the process of eliminating the obvious wrong ones or taking a clue from the most similar ones.
Hiya.
I use challenge 1 and 2 frequently but instead of using challenge 3 where I ask students to explain why the wrong answers are wrong, I ask them to explain why the correct answers are correct.
I find this focuses them on the mathematical conceptual understanding and also unearths reasons such as "I guessed." It's important to check how students get their answers. I have found challenge 2 quite useful in getting students to actually work out an answer rather than making a quick guess or a calculated guess where they arrive at an answer by the process of eliminating the obvious wrong ones or taking a clue from the most similar ones.