1.3. Measurement Systems
Measurement Systems
Metric system (SI – international system of units): the most widely used system of measurement in the world. It is based on the basic units of meter, kilogram, second, etc.
SI common units:
| Quantity | Unit | Unit symbol |
| Length | meter | m |
| Mass (or weight) | gram | kg |
| Volume | litre | L |
| Time | second | s |
| Temperature | degree (Celsius) | °C |
Metric prefixes (SI prefixes): large and small numbers are made by adding SI prefixes, which is based on multiples of 10.
Metric conversion table:
| Prefix | Symbol (abbreviation) | Power of 10 | Multiple value | Example |
| mega | M | 106 | 1,000,000 | 1 Mm = 1,000,000 m |
| kilo- | k | 103 | 1,000 | 1 km = 1,000 m |
| hecto- | h | 102 | 100 | 1 hm = 100 m |
| deka- | da | 101 | 10 | 1 dam = 10 m |
| meter/gram/litre | 1 | |||
| deci- | d | 10-1 | 0.1 | 1 m = 10 dm |
| centi- | c | 10-2 | 0.01 | 1 m = 100 cm |
| milli- | m | 10-3 | 0.001 | 1 m = 1,000 mm |
| micro | µ | 10-6 | 0.000 001 | 1 m = 1,000,000 µm |
Metric prefix for length, weight and volume:
| Prefix | Length (m – meter) | Weight (g – gram) | Liquid volume (L – litre) |
| mega (M) | Mm (Megameter) | Mg (Megagram) | ML (Megalitre) |
| kilo (k) | km (Kilometer) | kg (Kilogram) | kL (Kilolitre) |
| hecto (h) | hm (hectometer) | hg (hectogram) | hL (hectolitre) |
| deka (da) | dam (dekameter) | dag (dekagram) | daL (dekalitre) |
| meter/gram/litre | m (meter) | g (gram) | L (litre) |
| deci (d) | dm (decimeter) | dg (decigram) | dL (decilitre) |
| centi (c) | cm (centimeter) | cg (centigram) | cL (centilitre) |
| milli (m) | mm (millimeter) | mg (milligram) | mL (millilitre) |
| micro (µ) | µm (micrometer) | µg (microgram) | µL (microlitre) |
Steps for metric conversion:
- Identify the number of places to move the decimal point.
– Convert a smaller unit to a larger unit: move the decimal point to the left.
– Convert a larger unit to a smaller unit: move the decimal point to the right.
Example 1.3.1
326 mm = (?) m
- Identify mm (millimeters) and m (meters) on the conversion table.
Count places from mm to m: 3 places left
- Move 3 decimal places. (1 m = 1000 mm)
Convert a smaller unit (mm) to a larger (m) unit: move the decimal point to the left.
| 326. mm = 0.326 m | Move the decimal point three places to the left (326 = 326.). |
Example 1.3.2
4.675 hg = (?) g
- Identify hg (hectograms) and g (grams) on the conversion table.
Count places from hg to g: 2 places right
- Move 2 decimal places. (1 hg = 100 g)
Convert a larger unit (hg) to a smaller (g) unit: move the decimal point to the right.
| 4.765 hg = 476.5 g | Move the decimal point two places to the right. |
The Unit Factor Method
Convert units using the unit factor method (or the factor-label method)
- Write the original term as a fraction (over 1).
- Write the conversion formula as a fraction or .
- Put the desired or unknown unit on the top.
- Multiply the original term by or . (Cancel out the same units).
Example 1.3.3
1200 g =