Look at the rectangle on the board, filled with square tiles. Every tile is the same size. Is there a gap anywhere? Is any tile sitting on top of another?

You already know how to find the distance around a shape. Today we are measuring something new: the flat space inside it.

Three patches of the grid, each filled with square tiles. Every square is exactly the same size, so counting the tiles tells you the area.

The second one is an L-shape. Count carefully round the bend.

The last one is the important one. Two triangle tiles sit beside one whole square. Each triangle covers half a square, so the two of them together cover the same space as the whole square: two halves count as one square unit.

Your teacher outlines a shape on the grid. Click a square tile into every cell inside the outline, leaving no gaps and no overlaps.

Where the outline cuts straight across a square, use a triangle tile for that half. Two triangles count as one square unit, so pair them up as you count.

Then count the square units aloud and say the area in cm². The class checks that no square was missed or counted twice.

Now we cover four real outlines with square tiles and count the units. We work up in order: a 2-by-3 patch, then a 4-by-4 patch, then an L-shaped patch of 9 squares, and last a staircase shape that includes two half-squares to join. If you finish early, try to make two different shapes that both have an area of 10 squares.

What we learned

• Area is the flat space inside a shape, and we measure it by counting equal square units.
• We count whole squares, and join two half-squares to make one whole.
• We write area in square centimetres (cm²).

Coming up

Next we will spot that the squares sit in equal rows — so instead of counting one by one, we can multiply the rows by the columns.