SI Units of Length

SI Units of Length Prior Learning SI units of length include the meter, centimetre and millimetre. Conversion factors are used to convert a measure from one unit to another. This table shows the relationship among some of the units of length.

1 m = 100 cm 1 m = 1000 mm

1 cm = 0.01 m 1cm = 10 mm

1mm = 0.001 m 1 mm = 0.1 cm  To convert from meters to centimetres

Convert 7.3 m to centimetres. Since 1 m = 100 cm, to convert meters to centimetres, multiply by 100. 7.3 m = 7.3(100 cm) 7.3 m = 730 cm

 To convert centimetres to meters

Convert 225 cm to meters. Since 1 cm = 0.01 m, to convert centimetres to meters, multiply by 0.01. 225 cm = 225(0.01 m) 2252 cm = 2.25 m Check your understanding

1. Which SI unit of length is the most appropriate unit to measure each item? Justify your choice. a) the width of the hallway b) the height of my desk c) the length of a paperclip d) the length of an eyelash

2. Estimate each measurement in SI units. a) the length of your shoe b) the height of the class door c) the thickness of a nickel d) the width of an eraser

3. Convert each measure to centimetres. a) 9 m b) 36 mm c) 47.3 m d) 253 mm

4. Convert each measure to meters. a) 845 cm b) 4286 mm c) 95 cm d) 1100 mm

5. Convert each measure to millimetres. a) 3.5 cm b) 2.7 m c) 43 cm d) 0.9 m