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Grade 5 Math · Level 4, Solids, Volume & Data

Composite Volume & Additivity

How the lesson starts: Composite Volume & Additivity

1. Finn's Sandcastle Contest

   It's the beach sandcastle contest, and Finn builds a castle from sand blocks. His castle isn't one simple box. It's boxes stuck together! To find how much sand it holds, we split it into boxes and add.

2. Volumes add up

   Finn builds a tower: 4 by 3 by 4, that's 48 cubic units. Next to it, a low wall: 5 by 3 by 2, that's 30 cubic units. Joined without overlapping, the volumes just add: 48 + 30 = 78! And if a piece is cut away, subtract it.

3. Split the L

   Finn's next castle is shaped like an L. Split it into two boxes! The long base is 6 by 2 by 2: 24. The tall part on top is 2 by 2 by 4: 16. 24 + 16 = 40 cubic units. Watch out: find each box's volume first.