## The metric system

**imperial system**.

This was a reference to 'imperial' Britain, because that's where the system was first developed.

Length, for example, was measured in inches, feet, yards and miles.

Weight was measured in ounces, pounds, stone and tons.

The metric system is based on the **decimal system** of numbers. This means that all measurement units are based on multiples of 10.

For example, the standard unit of length is the **metre**. So the other units used to denote longer and shorter lengths are in multiples of 10 from the 'one metre' standard. Click on the link below to see the table of metric length units ranging from the millimetre (mm) to the kilometre (km).

Table of metric lengths from mm to km

Metres and kilometres are terms used by just about everyone, including in ordinary day-to-day conversations.

Millimetres are widely used in building, construction and manufacturing.

Centimetres are also common in particular fields.

But decimetres, decametres and hectometres have only limited usage in specialist areas.

### Learning activity

Audio 8 (mp3 |6|KB)Below is a table showing various lengths in kilometres (km) centimetres (cm) and millimetres (mm). Rewrite each of these measurements in metres, or proportions of a metre by entering the correct answers in the right hand column.

Remember that the decimal point is critical in metric measurements. If you're not sure where the point should go, refer back to the table of metric lengths.

It's also good practice to put a zero in front of the decimal point if the number is less than 1. That is, it's better to write '0.5' than '.5', because there is less chance of misreading the measurement when you come back to it later.

When you've finished, click on the 'Check your answers' button to see how you went.

Convert these measurements to metres | value | Unit of measure |
---|---|---|

1.5 km | 1500 | m |

1 km | 1000 | m |

1/2 km | 500 | m |

1/4 km | 250 | m |

350 cm | 3.5 | m |

185 cm | 1.85 | m |

4800 mm | 4.8 | m |

3660 mm | 3.66 | m |

900 mm | 0.9 | m |

255 mm | 0.255 | m |

75 mm | 0.075 | m |

25 mm | 0.025 | m |

9 mm | 0.009 | m |

3 mm | 0.003 | m |