B. The SI System
Explore the Lesson
B. The SI System
Earlier in this Unit, you were introduced to linear measurement units used in the SI system. The SI system also includes units for mass (kilograms), and capacity (litres), among others. Prefixes are used to represent different sized units and prefixes are related by powers of 10. For example, kilometres and centimetres are both derived from the metre. A kilometre is 1000 (103) times longer than a metre and a centimetre is 100 (102) times shorter than a metre.
The table below shows some commonly used prefixes and how they are related to the base units. The conversion factor shows how many of that unit make up the base unit. For example, there are 0.001 kilometres in a metre.
| Prefix |
Conversion
Factor |
Length | Volume | Mass |
|---|---|---|---|---|
| kilo | 0.001 | kilometre (km) | kilolitre (kL) | kilogram (kg) |
| hecto |
0.01 |
hectometre (hm) | hectolitre (hL) |
hectogram (hg) |
|
deca |
0.1 |
decametre (dam) | decalitre (daL) |
decagram (dag) |
| Base Unit |
1 |
metre (m) | litre (L) |
gram (g) |
| deci | 10 | decimetre (dm) | decilitre (dL) | decigram (dg) |
| centi | 100 | centimetre (cm) | centilitre (cL) | centigram (cg) |
| milli |
1000 |
millimetre (mm) | millilitre (mL) |
milligram (mg) |
Metric Conversions
In this Lesson you will explore three methods for converting between metric units. The first strategy uses a proportion, and can be used to convert between any pair of units, metric or not. The second strategy uses unit analysis and can also be used for any unit, metric or not. The third strategy uses the fact that metric units are related by powers of 10. This strategy can only be used with metric units.
Before reading any further, try to use the prefix table to complete the following statements. If possible, compare your strategy to that of another student.
-
25 L = _____ dL
-
157 mm = _____ m
-
12 kg = _____ mg