For example
The union of the singers and the drummers is everyone in either group.
In Grade 3
Children combine two sorted hoops of objects and count everything that ended up in either one.
Watch out for
Children often count the shared items twice in a union. Anything sitting in both groups is still counted only once.
Say it at home
Sort objects two ways and ask how many are in one group or the other altogether.
Try it together
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