The last two variants are correct. One unit on the map corresponds to 25000 of the same units IRL (in real life). In particular, 1 cm on the map corresponds to 25000 cm = 250 m = 0.25 km IRL. This works when units are kilometers as well, but it's less convenient to measure maps in kilometers.Is it 1cm = 25000 km or 1 km = 25000 km or 1cm = 25000 cm?