 ## Grade 4 Math: Units of Measure

### Metric System: Base Units

In this lesson, students begin to learn about the metric system of measurement. The metric system is based on base units and prefixes. There are two kinds of prefixes: those that are multiples of the base units and those that are fractions of base units.

In this lesson, students learn the base units for length, volume and weight. The meter is the base unit for length. The liter is the base unit for volume. The gram is the base unit for weight.

The size of these units relative to comparable measures in the U. S. Customary System is illustrated with examples. The meter is a little longer than a yardstick. A liter is a little more than a quart. A gram is about the weight of a raisin or a regular paperclip.

### Metric System Prefixes: Less than 1

In this lesson, students learn three prefixes for base units in the metric system: milli-, centi-, and deci-.

When used with a base unit, these prefixes create measures that are less than the base unit. Milli- means one thousandth of a base unit. Centi- means one hundredth of a base unit. Deci- means one tenth of a base unit.

### Metric System Prefixes: Greater than 1

In this lesson, students learn three additional prefixes for base units in the metric system: deka-, hecto-, and kilo-.

When used with a base unit, these prefixes create measures that are greater than the base unit. Deka- means tens times the base unit. Hecto- means 100 times the base unit. Kilo- means 1000 times the base unit.

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