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Chapter 3: Beyond Making 7—More Problems to Explore
Detailed answers to the nontrivial questions under the section below titled “For Your Own Learning” can be found in the companion website for this book at www.corwin.com/algebraprek–12.
You may be familiar with a first-grade, child-friendly addition algorithm sometimes called the “opposite-change” method (e.g., this phrase is used in early editions of the Everyday Mathematics curriculum). For example, you can solve the addition problem
by making a simple change in the first addend (add 1), and making the opposite change in the second addend (subtract 1). You could also add 2 to 18 and subtract 2 from 29. In either case, you obtain a zero in the ones ...