Bridge: Volume of Rectangular Prisms

How the lesson starts: Bridge: Volume of Rectangular Prisms

Ember's gem box
Hello there! Meet Ember, a friendly little dragon who collects shiny gem cubes. She wants to pack them into her treasure box with no gaps at all. How many cubes will fill it? That's called volume!
The bottom layer
Volume counts unit cubes, each 1 unit on every side. Ember starts at the bottom of the box. She lines up 3 cubes across and 2 cubes deep. That's 3 × 2 = 6 cubes in one layer.
Stack the layers
Now she stacks more layers, each with 6 cubes. Layer 1: 6. Layer 2: 12. Layer 3: 18. Layer 4: 24. Four layers of 6 make 24 cubes, even the hidden ones inside. The volume is 24 cubic units, not 3 + 2 + 4 = 9!