Relate subtraction from ten to corresponding decompositions.

In this lesson, students solve using Rekenrek bracelets and number bonds to show how "partners of 10" lead to related subtraction number sentences. For example, they notice that 10 - 3 = 7 and 10 - 7 = 3 are shown in similar ways with their Rekenrek bracelets (both starting with 10, and involving a group of 3 and a group of 7), and that knowing one subtraction sentence allows them to quickly know the other.