Building Plans in Cubeland

Display and direct students' attention to the Professor Peabody Is Confused Master. Have students follow Professor Peabody's building plan on the Master to make a cube model. Then tell them to consider his number sentence.

Brainstorm together and list several options that Professor Peabody could have used. Discuss how the numbers in the number sentences match the cubes in the model. Possible responses may include:

2 + 2 + 2 + 2 + 5 + 2 = 15 (adding all the columns)
6 + 6 + 1 + 1 + 1 = 15 (adding all the floors)
4 + 7 + 4 = 15 (adding from left to right)
6 + 9 = 15 (adding from back to front)

Next, direct students' attention to the "What If" Volume Problems pages in the Student Activity Book. Assign Questions 1–3. Have students work in pairs, with one student pretending to be Sara and one student pretending to be Sam. Have students share the strategies they can use to determine the new volumes once cubes are added to the original designs. Many students may be able to determine that when you add one story to each column, as in Sam's new building, they do not have to count from zero. They may look at their original building and add 9 cubes. Others will count all of them from the beginning again. Have students discuss what strategies they used first with their partner, and then with the class.

Finally, assign Check-In: Questions 4–6 for students to complete independently.