Today is rung 5 of 5 on this topic
Surface area and volume of solids
Can do: Finds surface area and volume of prisms, cylinders and composite solids.
Why it matters
It's where geometry meets real design questions — packaging, capacity, materials — and where units get tested properly.
What it looks like when it's wobbly
Mixes up which needs squaring and which cubing, and loses the units.
⏱️ Two-minute check
"A cylinder radius 3, height 10 — volume and surface area?"
Solid looks like: About 283 cubic units and about 245 square units, with units stated.
The full activity for this topic · 30 minutes
Design the Packaging
- 1Give a fixed volume — say 500 cm³ — and ask them to design a box that holds it.
- 2Calculate the surface area of their design, which is the material cost.
- 3Try a different shape with the same volume and compare the surface areas.
- 4Build the best one and check it physically.
- 5Discuss why real packaging isn't always the most efficient shape.
If it's too hard
One rectangular prism, both calculations.
If it's too easy
Compare a cylinder and a box of equal volume and explain which uses less material and why.
Say this
"Volume is what fits inside, surface area is the wrapping paper. Which one is the question asking for?"