The story in three lines. Tila marks out a patch for the hens, three squares by three. Tí counts the squares inside, nine, and fetches nine sticks, but the fence runs out on the third side. Fence the goat walks round the edge and counts twelve, so Tí fetches three more.

The five nights. Night one, listen. Night two, let your child say the bold last words. Night three, join in the refrains. Night four, stop when the fence is too short and ask why. Night five, tell it to a toy.

One thing to do at the table. Make a square of nine crackers or tiles, three by three. Now put spoons or pencils round the outside. How many do you need? Count the inside, then count the edge.

The answer. Nine inside, twelve round the edge. The inside and the edge are two different counts. Later, children call these area and perimeter.

The grown-up layer. Mixing up the inside and the edge is very common, even much later in school. ArrayPals' Fence keeps the two counts apart.

For the ride home. Ask: how many steps round the edge of the rug?