1. How are length and area measured?
Objective: Identify the SI and metric units used to measure length and area.
Vocabulary
Meter – basic SI and metric unit of length
Unit – amount used to measure something
Scientific Measurements
Measuring is an important part of science. The metric system is an international system of measurement. Most countries use the metric system of measurement. Their everyday measurements are given in metric units. A unit is an amount used to measure something.
Since 1960, scientists have used a modern form of the metric system called Systeme International, or SI. Most of the units in SI are the same as metric units.
Define: What is a unit?
Changing Units
Both the metric system and SI are based on units of ten. This makes these measurement systems easy to use. Each unit is ten times smaller or larger than the next unit. Prefixes are used to change the size of a unit.
Analyze: Use Table 1. What is the meaning of the prefix hecto-?
Units of Length
In the metric system, length and distance are measured in meters. The meter is the basic unit of length. A doorknob is about one meter from the floor. You can use prefixes to make longer or shorter lengths. For example, the prefix kilo- means One kilometer is equal to 1000 meters. Table 2 shows how prefixes can be used to make different lengths. Table 2 also shows the symbols for each unit.
Table 2
1000 meters (m) = 1 kilometer (km)
100 centimeters (cm) = 1 meter (m)
1000 millimeters (mm) = 1 meter (m)
Metric Prefixes and Values
kilo-
One thousand (1000)
hecto-
One hundred (100)
deca -
Ten (10)
deci-
One tenth (1/10 or 0.1)
centi-
One hundredth (1/100 or 0.01)
milli-
One thousandth (1/1000 or 0.001)
Calculate: How many millimeters are there in one centimeter?
Measuring Length and Area
Length and distance can be measured with a meter stick. A meter stick is one meter long. A meter stick is divided into 100 equal lengths by numbered lines. The distance between each of these lines is equal to one centimeter. Each centimeter is divided into 10 equal parts. Each one of these parts is equal to one millimeter.

2. Explain: How do you find the area of a rectangle?
Suppose you wanted to wallpaper a room. How would you know how much wallpaper to buy? You would need to know the area of each wall. You can find the area of a rectangle by multiplying its length by its width. Area is measured in square units, such as square meters (m2).
Explain: How do you find the area of a rectangle?
Lesson Summary
The metric system is an international system of measurement.
Scientists use SI
The metric system and SI are based on units of ten.
The meter is the basic unit of length in the metric system and SI
A meter stick is used to measure length.
The area of a rectangle is found by multiplying its length times its width.
Check Complete the following.
A _________ is an amount used to measure something.
In the metric system, the basic unit of length is the ________.
Each unit in the metric system is _____ times smaller or larger than the next unit.
You can find the ______ of a rectangle by multiplying its length by its width.
Scientists use a modern form of the metric system called _________.
Most countries use the ________ system of measurement.
A meter stick is divided into _______ equal lengths by numbered lines.
Apply Complete the following.
8. Calculate: What is the area of a rug that is 12 m long and 10 m wide?
9. Match each prefix with its correct meaning.
1. deca- a. one tenth
2. milli- b. one thousandth
3. centi- c. one hundred
4. deci- d. one thousandth
5. hecto- e. ten
6. kilo- f. one hundredth
10. Describe: What are the advantages of using the metric system or SI?