Every colourful page of Christopher Danielson’s children’s picture book, Which One Doesn’t Belong?, contains a thoughtfully designed set of four shapes. Each of the shapes can be a correct answer to the question “Which one doesn’t belong?” Because all their answers are right answers, students naturally shift their focus to justifications and arguments based on the shapes’ geometric properties.
Most curricula treat geometry as little more than vocabulary lessons. Which One Doesn’t Belong? is a powerful, flexible resources that teachers can use to provoke lively discussions and deep learning about shapes with students of all ages.