Are you familiar with Which One Doesn't Belong? (WODB)
It's one of my FAVORITE warm up activities! I love WODB because there is no single correct answer. Kids can come up with aaaaaanything they want as long as they can support their answer with reasoning.
I've found this routine gets more kids involved because they feel safe taking more risks. The fear of being wrong is eliminated! I love when my mathematicians come up with a response I hadn't even thought of. They get REALLY creative, and it's nice to see them get excited for each other.
Take a look at the WODB below. Which one do you think doesn't belong?
And don't worry 2nd-6th grade parents. Your book is in the works!