technical design/maps/geography
posted by Claire .
The scale of a map is 9mm represent 1km on real ground. I found the area of the map and it is 19990mm2. How am I going to use the scale to find the area of the real ground? Thanks a lot!

If the scale is 9mm/1km, then the area scale is that squared, or 81squaremm per 1 km^2

Thank you so much for your help!