Here is the corner of the school grounds where we could build a class garden bed.

If we wanted to build a bed 2 metres long and 3 metres wide, what three different things would we need to measure or work out before we could actually build it and fill it with soil?

Watch two garden beds on the board. The first is a plain 2 m by 3 m rectangle. To find the edging, add the four sides: 2 + 3 + 2 + 3 = 10 m. To find the growing space inside, multiply length × width: 2 × 3 = 6 m².

Now watch the same bed shown as a solid, filled to a depth of 0.3 m. The soil is the growing space × the depth: 6 × 0.3 = 1.8 m³.

Some beds are not simple rectangles. Here is an L-shaped bed. We can draw one straight line to split it into two rectangles you already know how to measure, and the two areas add together to give the whole.

Today we design one garden bed together and measure it three ways. We'll work through these on the board:

1. Drag the corners to make the bed 4 m long and 2 m wide.
2. Read the edging round the outside and the growing space inside.
3. Switch to the solid view and fill it to a depth of 0.3 m to find the soil.
4. Stretch the bed to 5 m by 2 m and watch every number change.

Now design your own garden bed and prove it works, one design at a time. We'll work these together on the board.