Lesson 2

Students are introduced to rectangular prisms as they begin to informally use the structure of rectangular prisms to find the number of cubes in the prism. In previous grades, students learned to measure area by counting unit squares, decomposed a rectangular region into rows and columns, and multiplied the number of unit squares in a row by the number of rows or the number of unit squares in a column by the number of columns. Similarly, in this lesson, students make use of the layered structure in a rectangular prism to count the cubes in a more systematic way (MP7). Students will have many opportunities to count the number of cubes in rectangular prisms in lessons 3 and 4 before the introduction of formulas in Lesson 5.

Math Community

Tell students they will have an opportunity to revise their “Mathematical Community” ideas at the end of this lesson, so as they work today they should think about actions that may be missing from the current list.

• Each group of 2 needs 24 connecting cubes.

• Each group of 2 needs 16-24 connecting cubes.

What did students understand about the volume of solid objects as they came into the lesson? In what ways did their understanding of volume change upon completing the lesson?