chapter 7 measurement © 2010 pearson education, inc. all rights reserved

Chapter 7

Measurement

© 2010 Pearson Education, Inc.All rights reserved.

7.2 The Metric System - Length

Objectives

Slide 7.2- 2

1. Learn the basic metric units of length.

2. Use unit fractions to convert among units.

3. Move the decimal point to convert among units.

Copyright © 2010 Pearson Education, Inc. All rights reserved.

2- 3

The basic unit of length in the metric system is the meter. Use the symbol m for meter, do not put a period after it. To make longer or shorter units in the metric system, prefixes are written in front of the word meter. The table below shows how to use the prefixes for length measurement.


2- 4

Here are some comparisons with commonly used length units: km, m, cm, mm.

Kilometer – Used instead of a mile. A kilometer is 1000 meters. It is about 0.6 mile.

Centimeter – Used instead of inches. A centimeter is 1/100 of a meter. It is a little shorter than ½ inch. The width of your little finger is about 1 cm.

Millimeter –A millimeter is 1/1000 of a meter. The thickness of one dime is about 1 mm.


ParallelExample 1

Using Metric Length Units

Slide 7.2- 5

Write the most reasonable unit in each blank. Choose from km, m, cm, and mm.

The distance from your office to your home is 30 ________.

a.

b.

30 km because kilometers are used instead of miles. 30 km is about 18 ½ miles.

The thickness of cardboard is 3_____.

3 mm because the thickness of cardboard is very small.

c. The length of your calculator is 18 _____ long.

18 cm which is about 7 inches. Copyright © 2010 Pearson Education, Inc. All rights reserved.

ParallelExample 2

Using Unit Fractions to Convert Length Measurements

Slide 7.2- 7

Convert each measurement using unit fractions.

7 km to metersa.

Unit fraction equivalent to 1

Multiply. Divide out common units where possible.

1000 m

1 kmUnit for answer

Unit being changed

1000 m7 km

1 km

7 1000 mk

1

m

km1

7 1000 m

1

7000 m

These units should match.

7 km = 7000 m Copyright © 2010 Pearson Education, Inc. All rights reserved.

ParallelExample 2continued

Using Unit Fractions to Convert Length Measurements

Slide 7.2- 8

Convert each measurement using unit fractions.

92.7 cm to mb.

Multiply by a unit fraction that allows you to divide out centimeters.

9 cm

cm

2.7 1m

1 100

92.7 m

100 0.927 m

92.7 = 0.927 m

There are 100 cm in a meter, and 92.7 cm is almost a meter. The answer makes sense.


2- 9

An alternative conversion method to unit fractions is moving the decimal point using this metric conversion line.


ParallelExample 3

Using the Metric Conversion Line

Slide 7.2- 10

Use the metric conversion line to make the following conversions.

4.658 km to ma.

Find km on the metric conversion line. To get to m, you move three places to the right.

km hm m dm cm mmdam

Three places to the right. 4. 6 5 8Move the decimal point three places to the right.

4.658 km = 4658 m Copyright © 2010 Pearson Education, Inc. All rights reserved.

ParallelExample 3continued

Using the Metric Conversion Line

Slide 7.2- 11

Use the metric conversion line to make the following conversions.

49.7 cm to mb.

Find cm on the metric conversion line. To get to m, you move two places to the left.

km hm m dm cm mmdam

Two places to the left. 4 9 . 7Move the decimal point two places to the left.

49.7 cm = 0.497 m Copyright © 2010 Pearson Education, Inc. All rights reserved.

ParallelExample 4 Practicing Length Conversions

Slide 7.2- 12

Convert using metric conversion line.

29 cm to ma.

From cm to m is two places to the left. The decimal point starts at the far right because 29 is a whole number. Then move it two places to the left.

2 9. 29 cm = 0.29 m

b. 5.18 cm to km

From cm to km is five places to the left.

0 0 0 0 5.1 8. 5.18 cm = 0.0000518 km

b. 5.18 cm to km


chapter 7 measurement © 2010 pearson education, inc. all rights reserved

Documents