Throughout the unit, students have made sense of the ways equations, including those with symbols for an unknown, represent story problems or ways to solve them. In previous lessons of this unit, students matched equations to story problems and wrote their own equations. Although lesson activities as early as kindergarten introduce equations in which the total or difference is on the left side of the equal sign (for example or ), students are most familiar with equations in which the total or difference is on the right side. This can lead to misconceptions about what the equal sign or equations themselves mean.

In this lesson, students are encouraged to deepen their understanding of equations and the meaning of the equal sign. First, students revisit the Shake and Spill center and generate equations where the total is on the left or right side of the equal sign. Then students work with a new center called Number Puzzles. This center includes equations with the total on the left or right side of the equation and gives students the opportunity to practice explaining how they know an equation is true.

Both Stage 2 and Stage 3 of the Shake and Spill center are revisited with a focus on a total of 10 to provide additional practice with sums of 10 before students work with place value in the next unit. This also provides a way for students to show how they may use known facts to determine unknown values. In order to ensure there is time for introducing Number Puzzles, consider introducing the idea of recording rounds of Shake and Spill with equations using Stage 3, but allowing students to choose whether to work on Stage 2 or Stage 3. Focus the Lesson Synthesis on sharing and comparing equations as is recommended in the Synthesis of the first activity.

Think about which students haven’t shared their thinking in class lately. Were there missed opportunities to highlight their thinking during recent lessons? How can you take advantage of those opportunities when they arise?