Today is rung 3 of 6 on this topic
Volume of solid figures
Can do: Finds the volume of a rectangular prism by counting cubes and by multiplying length × width × height.
Why it matters
It's the first three-dimensional measurement and it makes cubic units — and cubed notation — concrete.
What it looks like when it's wobbly
Uses area formulas on 3-D shapes, or gives the answer in square units.
⏱️ Two-minute check
"A box is 4 by 3 by 2. What's its volume? What are the units?"
Solid looks like: 24 cubic units, with cubic said explicitly.
The full activity for this topic · 20 minutes
Fill the Box
- 1Fill the base of a box with cubes and count them — that's the area of the base.
- 2Count how many layers fit. Volume is base × layers.
- 3Write the formula only after they've seen it: length × width × height.
- 4Measure a real box and calculate before filling it, then check.
- 5Compare two boxes with the same volume but different shapes.
If it's too hard
Count the cubes physically without a formula.
If it's too easy
Find a missing dimension given the volume, or the volume of two prisms joined together.
Say this
"How many fit on the bottom layer? How many layers? That's the whole formula."