The Thursday Packet (two printable pages). Page one is the letter: "Your globe is ready. Collect it from our shop at C4. We are three hundred metres north of the fountain." Page two is a map with columns A to F along the bottom, rows 1 to 6 up the side, a fountain in square C4, a scale bar where one centimetre is a hundred metres, and a north arrow. A faint pencil line runs three centimetres north from the fountain.

Try it before chapter 6. Find C4 (letter first). Measure the pencil line and use the scale bar. Turn the map so north points north.

The answer. The fountain is in C4. Three centimetres is three hundred metres. The shop is three hundred metres north of the fountain. Anyone who walked to 4C, or held the map upside down, gets a second go. No points are lost.

No printer? Draw a six-by-six grid on paper, label it, and mark the fountain in C4.

The grown-up layer. Grid references, map scale and orientation are three separate skills, and mistakes usually come from mixing them up. Reading the column first is a convention, which is why "along the corridor, then up the stairs" helps. MapForge plays with all three.

For the ride home. Ask: what are the two ways the company could have gone wrong?