Which One Doesn’t Belong is a website dedicated to providing thought-provoking puzzles for math teachers and students alike. There are no answers provided as there are many different, correct ways of choosing which one doesn’t belong. Enjoy!

“The concept is simple: there are four numbers, shapes, or graphs, and you have to find a reason each one is the odd one out. If the numbers are 9, 16, 25, and 43, you could say 9 is the odd one out because it has only one digit, 16 is the odd one out because it’s not odd, 25 is the odd one out because it does not end in a multiple of three, or 43 is the odd one out because it is not a square. There is no right answer, and each activity can be a jumping-off point for mathematical creativity”