How to play Which One Doesn't Belong?
- Look at the four numbers.
- Choose one that you think does not belong and explain why.
- Look for another reason that makes a different number the odd one out.
- Press Reasons we found to see some ideas, or make your own set.
Maths skills this game builds
- Reasoning and justifying
- Number properties: odd, even, prime, square, multiples
- Mathematical language
- Listening to other ideas
Tips for parents and carers
- There are many right answers. Ask “Can you find a different reason?”
- Make a set for a family member to try.
- Look at numbers on a car registration plate and find odd-ones-out.
Using Which One Doesn't Belong? with a group or class
- Show a set and give children a minute to think. Ask for different reasons from different children.
- Praise explanations that use mathematical words such as “multiple” or “prime”.
- Children can make their own sets for the group to solve.
Frequently asked questions
Is there only one right answer?
No. Every number can be the odd one out for a different reason.
What makes a good reason?
One that is true and clearly uses a mathematical idea, such as “it is the only odd number”.
Can I use my own numbers?
Yes. Type four numbers separated by commas.