Converting Lengths

Converting Metric Lengths to other Metric Units

Centimetres to Millimetres and Back Again

Each centimetre is made up of \(10\) millimetres.

To convert a measurement from centimetres to millimetres, you need to multiply it by \(10\). For example, a measurement of \(23\) centimetres would convert to \(23 \times 10 = 230\) millimetres.

To convert a measurement from millimetres to centimetres, you need to remember that the millimetre is the smaller unit, so you need to divide by \(10\). A measurement of \(366\) millimetres would become \(366 \div 10 = 36.6\) centimetres.

Metres to Centimetres and Back Again

Each metre is made up of \(100\) centimetres. So, to convert a length measurement from metres to centimetres, you simply need to multiply it by \(100\). For example, Sam and Jasmin's table top has a length of \(1.7\) metres. This is \(1.7 \times 100 = 170\) centimetres.

To convert a measurement from centimetres to metres, you need to remember that each metre is made up of \(100\) centimetres, so you need to divide your measurement by \(100\). For example, a measurement of \(280\) centimetres would become \(280 \div 100 = 2.8\) metres.

Metres to Millimetres and Back Again

We know that there are \(100\) centimetres in a metre and \(10\) millimetres in a centimetre. Combining these two facts together tells us that there are \(100 \times 10 = 1,000\) millimetres in a metre.

To convert a measurement from metres to millimetres, simply multiply it by \(1,000\). The length of Sam and Jasmin's table top is \(1.7 \times 1,000 = 1,700\) millimetres. Its width is \(1.2 \times 1,000 = 1,200\) millimetres.

Sometimes, we need to convert measurements in millimetres to measurements in metres. To do this, remember that millimetres are smaller than metres and divide the number of millimetres by \(1,000\). For example, a measurement of \(12,500\) millimetres would convert to a measurement of \(12,500 \div 1,000 = 12.5\) metres.

Metres to Kilometres and Back Again

There are \(1,000\) metres in one kilometre.

To convert a distance from kilometres to metres, multiply by \(1,000\). For example, a distance of \(3.8\) kilometres would convert to a distance of \(3.8 \times 1,000 = 3,800\) metres.

To convert a distance from metres to kilometres, we need to divide by \(1,000\) (metres are smaller than kilometres). So, if someone told you that the distance from their home to their school was \(2,600\) metres, you could convert this to a distance of \(2,600 \div 1,000 = 2.6\) kilometres.

Example: Doing Conversions in Geometry Problems

Converting between Metric and Imperial Length Units.

We can convert between metric and Imperial lengths using similar methods. We just need to know what number to multiply each unit by to give the conversion.

For example, one foot is \(0.3048\) metres. So, to convert a length of \(10\) feet to metres, we simply multiply it by \(0.3048\) to give \(10 \text{ feet} = 10 \times 0.3048 = 3.048 \text{ metres}\).

You can convert a distance in kilometres into miles by multiplying it by \(0.6214\). So, a distance of \(100\) kilometres is equal to \(100 \times 0.6214 = 62.14\) miles.

As a final example, one inch is the same as \(25.4\) millimetres. So, a \(10\) inch long piece of ribbon is a piece of ribbon that is \(10 \times 25.4 = 254\) millimetres long.

You can do similar conversions between any Imperial unit of length and any metric unit of length, and vice versa. You just need to know the conversion factors (numbers to multiply by). Have fun!