Rectangular Prism Volume

How the lesson starts: Rectangular Prism Volume

Maya's Aquarium
Maya runs the town aquarium. She's setting up new fish tanks, and she needs to know how much water each one holds. Counting cubes one at a time takes forever! Let's learn a super fast way: a volume formula.
Length × width × height
Fill a small tank with unit cubes. It's 4 long and 3 wide, so the bottom layer holds 12. Stack a second layer: 24. That's 4 × 3 × 2 = 24 cubic units. Volume is length times width times height!
Base times height
Another shortcut: the bottom of a tank is its base. If the base area is 24 cm² and the water is 7 cm deep, volume = base × height. 24 × 7 = 168 cm³. It's the same as l × w × h, because l × w is the base!