The Common Core State Standards for Mathematics (CCSSM) drive the curricular and instructional decisions for most teachers in the United States (CCSSI 2010). Division in fourth grade is a major hurdle for many students, and CCSSM has placed the third-, fourth-, and fifth-grade division standards in the Number and Operations in Base-Ten (NBT) domain. Base ten is not a new term, but its emphasis in CCSSM has revived attention to this foundational characteristic of our place-value system. In addition to content standards, teachers of K–grade 12 must also implement eight Standards for Mathematical Practice (SMP). Two of these practices, Use appropriate tools strategically (SMP 5, CCSSI 2010, p. 7) and Look for and make use of structure (SMP 7, p. 8), guide teachers’ choices of appropriate instructional strategies and materials.

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