For example
Thirteen is a prime number: you cannot arrange thirteen bottle caps into equal rows.
In Grade 4
Children test numbers by trying to build equal rows, finding the ones that make only a single row.
Watch out for
Children often call one a prime number. A prime has exactly two different factors, and one has only itself.
Say it at home
Take a handful of objects and ask whether they make equal rows in more than one way.
Try it together
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