Area and perimeter: fencing a kitchen garden
Shape a vegetable garden with a 24 m roll of fence and find which rectangle grows the most vegetables.
Core concept
In short: Use the same fence to make different gardens and see which holds the most space.
Perimeter is the length around a shape and area is the space inside; the same perimeter can hold different areas
Topic: Area and perimeter
A family wants a rectangular kitchen garden (karesabari) and has a 24 m roll of fence. The fence goes all the way around, so the fence needed is the perimeter: The total distance around the edge of a shape. All key words: 2 × (length + width). The ground inside is the area: How much flat space a shape covers, measured in square units like cm². All key words: length × width, measured in square metres (m²), one bed of seedlings for each square metre. Two gardens can use exactly the same fence and still hold very different numbers of beds.
What you will learn
- Find the perimeter of a rectangle as 2 × (length + width).
- Find the area of a rectangle as length × width, in square units.
- Show that rectangles with the same perimeter can have different areas.
Before you start
- Multiply and add whole numbers.
Materials
- Squared paper and a pencil
Equipment
- A measuring tape
Procedure
- Drag the right side of the garden to change its length, and the top side to change its width.
- Count the beds (square metres) and the fence used, and compare them with the formulas.
- Use the whole 24 m roll for a long thin garden, and then for the garden with the most beds.
- Make a garden of exactly 24 m² with the least fence, and another 24 m² garden that needs more.
How this simulation is simplified
- The garden is a rectangle measured in whole metres.