Among geographers’ many tools, the one likely to come to mind first is the map. Maps provide us with a generalized picture of all or part of Earth’s surface. A large-scale map shows a small area in more detail than a small-scale map that may show Earth’s entire surface, but include only very large features.
A common map that is useful to everyone is the highway map. Highway maps help us find our way from place to place; they often identify parks or sites of historic interest; and they always include a scale to estimate distance.
If a map has a scale of 1:100,000, it means that 1 centimetre on the map represents 100,000 centimetres (the same as 1 kilometre) in real life. The scale allows you to say how big a real-life object is if you know how big its picture is on the map, as well as how big something should be on the map if you know its size in real life.
The key to doing scales sums is to remember that multiplying by numbers bigger than one makes things bigger and dividing by numbers bigger than one makes things smaller.