Here is a road sign on the way west. It reads Gaillimh 8 km. How far do you think a kilometre is? Would it take more steps than walking right across our yard, or fewer? Hands up if you think it is longer than the yard.

The converter shows a ladder with kilometres above metres and a ×1,000 tile between them. Look at each conversion on the ladder, from kilometres down to metres and back up. For each one, say your answer first. Then we tap the unit we are converting to, and the digits slide into place to check.

Today we work through four conversions together, reading each one off a signpost. All four go the same way, from kilometres down to metres: 4 km, then 7 km, then 2 km, and finally 5 km. Before each pupil sets the ladder, the whole class gives a quick signal — thumbs up if we multiply (km to m), thumbs sideways if we would divide. Then we say the answer aloud and check it on the ladder.