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How Does Scale Ratio Work?


Scale is a tool you use when you are looking at maps, for example. For a map to have any purpose, it has to be scaled down. It needs to fit on a sheet of paper or on the screen of your PC.

A scale is written like this: 1 : 10000. This means that 1 cm on the map or drawing will correspond to 10000 cm in real life. So the first number says something about what you measure on the map, while the second number tells you how much it is in reality.

Scale can work the other way as well, to make things bigger. For example, we can write the scale like this: 100 : 1. Then, 100 cm on the drawing will correspond to 1 cm in reality. Can you imagine anything you can draw blueprints of? It could be the components inside an iPhone, a room in a house, or a car.

The math master pointing towards a globe

Example 1

There is 6cm between Bergen and Oslo on a map. In reality the distance between the two cities is 300km. What is the scale of this map?

First, you have to find how many centimeters are in 300 km: 300km = (300 1000)m = 300000m = (300000 100)cm = 30000000cm

This means 6 cm on the map corresponds to 30000000 cm in reality. Then you can find the scale like this: 6 ÷ 30000000 6 6 ÷30000000 6 1 ÷ 5000000

The scale is 1 : 5000000.

Example 2

A globe has a radius of 20cm. The radius of the earth is approximately 6371km. What is the scale of the globe?

First, you need to find how many centimeters are in 6371 km: 6371km = (6371 1000)m = 6371000m = (6371000 100)cm = 637100000cm

That means 20 cm on the globe is equivalent to 637100000 cm in reality. Then you can find the scale like this: 20 ÷ 637100000 20 20 ÷637100000 20 1 ÷ 31855000

The scale is 1 : 31855000.

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