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This activity has been particularly created as a possible follow-on to More Children and Plants.
Then take this further by having five sets with the extra set having just 1 object.
You'll be able to think of your own examples too.
Perhaps most important is to formulate some generalisations that can be tested.
If you want a start to see one solution click "show"
If you want to see a solution for 5 sets 3, 4, 5, 6, 7 using 12, click "show"