Topics · Shapes & Measurement
Area and perimeter
Perimeter is the distance around a shape. Area is the space inside. Two shapes can share one and differ in the other.
Fences, floors, wrapping paper — this is measuring for real.
More ways into this idea
- Play with itFence SandboxTwo pens, four dials — grass and fence disagree
Step into a storyA Pen for PipSame grass, less fence — if you pick the right shape.- Step into a storyThe Stage PlanSame floor for dancing. Very different bill for the lights.
- Make it a gameSame Area, Different FenceBuild rectangles to order — the geometry is the judge
- Test yourselfA fresh mixed set, whenever you likeExplanations after every question. Nothing is recorded.
Common sticking points
- A common sticking point is mixing up area and perimeter. One is the space inside, the other the distance around — and same area doesn't mean same perimeter.
- Another is using metres for area. Area counts SQUARES, so it needs square metres; plain metres measure lengths, like the fence.
- For parallelograms, the slanted side is not the height. The height stands straight up from the base — slide the corner across and the shape becomes a rectangle.
Try this together
Lay out 24 coins as a 4 × 6 rectangle, then as 3 × 8. Ask: is there the same amount of coins-space? Now trace around each with a finger (or string). Was the trip around the same? (24 both times inside — but 20 vs 22 around!)
1–5 minutes, no materials to buy, nothing to hand in.
Ontario curriculum details
- E2.5Build the area formulas for parallelograms and triangles
- E2.6Same area, different perimeter — and solve problems with both
Plain-language summaries. See the full curriculum for every expectation and the official source.