Geometry // Volume Narrative Step 2

Visualizing Marked Prisms

Moving from Units to Groups

Material Analysis

Large rectangular prism (blue or grey), yellow prisms marked with tick marks for volume, single 2cm unit cube, tickets and labels.

Presentation

Arrange the yellow marked prisms alongside the solid prism. Point out the tick marks.

"Look at these yellow prisms. They are as long, as wide, and as tall as our grey prism. Notice these marks along the edges. If we drew lines between these marks, what shapes would we see on the face?"

FIG 2.1: COMPARING SOLID AND MARKED PRISMS

Place the 2cm unit cube against one of the squares on the marked face.

"This cube fits exactly inside one square. And our prism is exactly one cube tall. So if we count 50 squares on the base, we have 50 unit cubes of volume."

Line up five identical marked prisms and skip count.

"If each one is 50, then we can count: 50, 100, 150, 200, 250! The volume of our whole prism is 250 unit cubes."

"This lesson is the bridge. If the children don't believe the squares represent cubes, let them build the prism with unit cubes first to prove it to themselves."