Which One Doesn't Belong? Math Models

Look at this set of four pictures. Decide which one doesn’t belong with the other three. Use math words to describe your thinking. There are many ways to think about each one!

A. shows a number rack with 4 red beads on top and 1 red bead below. B. shows a 5-frame with 2 red dots and 3 blue dots. C. shows a 10-frame with 5 red dots in the top row and 2 blue dots in the bottom row. D. shows 2 hands. One holds up 2 fingers. The other holds up 3 fingers.


See if you can find reasons why each of the pictures might not belong with the other three.


Explain your thinking to someone else. Do they have different reasons for why one doesn't belong?