London is a very big place, and a map of it must be small enough to hold in your hand – an area of almost 1000 square miles must be scaled down so that it can fit on much less than 1 square metre of paper. The scaling here is typically 1:200,000 but may not be expressed in these units. We may be told 1cm:1km. 1:200000 and 1cm:2km are the same scale with different units:
We may be given the scaling in either form and have to know how to move from one to the other. To scale for example from 1cm:5miles to a form independent of units:
The road from London to Leicester is 7cm on the map. The scale of the map is 1:200000 . Find the distance from London to Leicester in miles.
The distance from London to Leicester is 7*18.75=131.25 miles.
The distance from Edinburgh to Glasgow is 70km. On a 1:100000 map find the distance.
so 70km is represented by 70cm on the map.