The Mouse-Proof Shelf

To reflect on the work in this lesson and give students more opportunities to compare and order quantities, display 4–5 number sentences and ask students to place them in order from smallest sum to largest sum. For example:

• 6 + 9
• 8 + 5
• 4 + 7
• 8 + 9

Have students write the sums next to each number sentence to make it easier to order them. Students can verify their order by using connecting cubes and a two-pan balance. Demonstrate how to start with the smallest sum and move up to the largest sum. Explain that for these number sentences, the two sides will not be balanced as they were for the Jill, Sally, Marty, and Bob Did It pages. The side with the smaller sum (and cube mass) will go up and the side with the larger sum (and cube mass) will go down.