Topic E leads students to a very intentional understanding and application of the equal sign and the commutative property of addition. Lessons 17 and 18 ask students to use pictorial representations (pictures and 5-groups) to write expressions and demonstrate that they are equivalent by using the equal sign. This work with the equal sign precedes the lessons on commutativity in order to allow students to construct true number sentences such as 4 + 3 = 3 + 4 without misunderstanding the equal sign to mean that the numbers are the same. Students understand that when added together, two numbers make the same total, regardless of whether one of the numbers appears first or second in equations and expressions. The topic ends with Lesson 20, where students directly apply their understanding of commutativity by starting with the larger quantity and counting on (a Level 2 strategy) as a matter of efficiency, “I can count on 2 from 7 when I solve 2 + 7!”
Learn about addition, subtraction, and making amounts equal to the Odd Squad. When Ms. O and O'Donahue visit the Mathroom, she is excited to see her old friend and help with the case.
