Take two cards and work out what the third one would have to look like.
For each feature: if the two are the same, the third must be too. If they differ, the third must be the remaining option.
Then look for exactly that card. For any pair of cards there is always only one matching third card.
Example
- 1, 4, 5
- 1, 2, 3
- 1, 3, 4
For parents
What does this exercise practice?
Finding trios practises paying attention to several features at once - a first step towards systematic sorting and classifying.
Common pitfalls
Usually only the shape gets noticed. A trio must follow the rule for number, shape AND filling - all three count.
How to practice at home
Use building blocks of different shapes and sizes to build groups of three where everything is the same or everything is different.