Which One Doesn't Belong is a great classroom discourse routine. Students choose the one that doesn't belong and justify what makes it different from the others.
WHY SHOULD YOU USE WHICH ONE DOESN'T BELONG?
Which One Doesn't Belong fosters Mathematical Discourse and provides the opportunity for students to use previous mathematical knowledge and understanding to construct viable arguments. When used strategically, there could be a specific skill that students use to determine which one doesn't belong. However, the beauty is in students using their own Mathematical Understanding to choose. Teachers can get valuable data about what their students know as they discourse and justify what doesn't belong with the others.
HOW CAN YOU USE WHICH ONE DOESN'T BELONG?
Which One Doesn't Belong is the perfect Math Warm-Up. The open-ended thinking and discourse warms up students minds prior to a math-lesson. It also works well for time-fillers & cool-downs after a lesson.
There are two ways that I sometimes extend the activity to push my students more.
I typically now have students to find the one on their own, collaborate as a group, and then the group choose the one that they want their group to say and they can only chose 1, which means that each member has to really justify in order to have theirs chosen as their group "representative."
Sometimes, I allow students to choose which one is out and justify it and then tell them that they have to choose another one and justify it.
Ensure that students are not just saying something about the one that doesn't belong, but what makes it different from the others. I redirect them if they say a number doesn't belong because it's the greatest number. I tell them that I can argue the lowest one doesn't belong. To really get the most out of the activity students need to not identify characteristics in one number that it makes it different, but similarities in the other three numbers that make them the same.
Require grade appropriate justification. For instance, I once had a student justify a number didn't belong because the other numbers included a 5, but it didn't. Although that was true, identifying digits Isn't an appropriate grade-level skill. (However, identify digits value using place value understanding is.)
ALL-INCLUSIVE STANDARDS ALIGNMENT:
THE ALL-INCLUSIVE CLASSROOM: D-1.2. High-Quality Academic Instruction: Purposeful, content-specific discourse among students.
ALL-INCLUSIVE MATH INSTRUCTION: D-1.2.B. Discourse: Classroom Routines.
I first saw which one doesn't belong on Pinterest.