1. Units of length When measuring the length of something or the distance between places, you have to choose an appropriate unit of length. There are four units of length that are used in the metric system. Metres (m)Metres are the standard unit of length. You would measure the length of a floor in metres. Centimetres (cm)A centimetre is used to measure smaller lengths such as the height of your school table. Metres are divided into 100 cm. Millimetres (mm)Millimetres are used to measure very small lengths such as the length of an insect. Centimetres are divided into 10 mm. Kilometres (km) Kilometres are used to measure large distances such as the distance between two countries. There are 1000 metres in 1 kilometre. There are other units of length out with the metric system that are commonly used, including miles. Miles are also used to measure long distances. 1 mile is roughly equal to 1600 metres or 1.6 km.

2. Units of length What would be the best unit of length to use to measure the following? The length of a swimming pool The width of a fingernail The distance from Glasgow to London The length of a banana The width of an iPod The width of a nail The distance between Ibrox and Parkhead The height of Big Ben Metres Millimetres Kilometres Centimetres Millimetres Kilometres Metres Now try question 1 in your booklet.

3. Units of length Each of the units of length that we looked at in the first slide can be broken down and described using alternative units of length. We have already seen that there are 1000 metres in a kilometre, and roughly 1600 metres in a mile so we will look at centimetres and metres now. Metres (m)There are 100 centimetres in 1 metre. Centimetres (cm)There are 10 millimetres in 1 centimetre. How many centimetres are there in 2 metres?200 centimetres How many millimetres are there in 50 cm?500 millimetres How metres are there in 6 kilometres?6000 metres

4. Measuring lengths There are a number of devices that you can use to measure lengths. A ruler allows you to measure small lengths in both centimetres (cm) and millimetres (mm). The longer lines on a ruler show centimetres. The smaller lines on a ruler show millimetres. To measure in metres you can use a tape measure, a metre stick or a trundle wheel. To measure in kilometres you can use a car odometer These are just a few devices that you can use. Now try question 2 in your booklet.

5. What would be the best device to use to measure the following? The length of a swimming pool The width of a fingernail The distance from Glasgow to London The length of a banana The width of an iPod The width of a nail The distance between Ibrox and Parkhead The height of a door Trundle wheel Ruler Odometer Tape measure Ruler Odometer Tape measure Now try question 3 in your booklet. Measuring lengths

6. Using a ruler Rulers usually show centimetres and millimetres. 0 mm 10 20 30 40 0 cm 1 2 3 4 This line is 3.5 cm or 35 mm or 3 cm 5 mm. As you can see, 1 cm is split into 10 parts called millimetres. 1cm = 10mm This line is 4.1 cm or 41 mm or 4 cm 1 mm. It is vital when measuring something with a ruler that you start at 0.

7. Using a ruler What length are these arrows pointing to in cm and mm? 0 mm 10 20 30 40 0 cm 1 2 3 4 abcdefgh a0.4 cm, 4 mm, 0 cm 4 mme2.4 cm, 24 mm, 2 cm 4 mm b0.8 cm, 8 mm, 0 cm 8 mmf2.9 cm, 29 mm, 2 cm 9 mm c1.5 cm, 15 mm, 1 cm 5 mmg3.6 cm, 36 mm, 3 cm 6 mm d2 cm, 20 mm, 2 cm 0 mmh4.3 cm, 43 mm, 4 cm 3 mm

8. Millimetres In industrial settings, even large objects are measured in millimetres. This is to ensure that measurements are made very accurately, which is vital in construction. Sometimes the success of a project might rely on an object being 123 mm rather than 125 mm. 450 mm 205 mm All car parts are measured in mm rather than cm. Now try questions 4 to 8 in your booklet.

9. Test yourself You are now ready to tackle the end-of-topic test in your booklet. GOOD LUCK!!