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Chp 8 Workbook

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NAME DATE PERIOD<br />

8-1<br />

Study Guide and Intervention<br />

Geometric Mean<br />

Geometric Mean The geometric mean between two numbers is the positive square<br />

root of their product. For two positive numbers a and b, the geometric mean of a and b is<br />

the positive number x in the proportion −<br />

a x = −<br />

x b . Cross multiplying gives x2 = ab, so x = √ ab .<br />

Example<br />

Find the geometric mean between each pair of numbers.<br />

a. 12 and 3<br />

x = √ ab<br />

= √ 12 . 3 a = 12 and b = 3<br />

Definition of geometric mean<br />

= √ (2 . 2 . 3) . 3 Factor.<br />

= 6 Simplify.<br />

The geometric mean between 12 and 3 is 6.<br />

b. 8 and 4<br />

x = √ ab<br />

= √ 8 . 4 a = 8 and b = 4<br />

= √ (2 . 4) . 4 Factor.<br />

= √ 16 . 2 Associative Property<br />

Definition of geometric mean<br />

= 4 √ 2 Simplify.<br />

The geometric mean between 8 and 4<br />

is 4 √ 2 or about 5.7.<br />

Lesson 8-1<br />

Exercises<br />

Find the geometric mean between each pair of numbers.<br />

1. 4 and 4 2. 4 and 6<br />

Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.<br />

3. 6 and 9 4. 1 −<br />

2 and 2<br />

5. 12 and 20 6. 4 and 25<br />

7. 16 and 30 8. 10 and 100<br />

9. −<br />

1 2 and −<br />

1 4<br />

10. 17 and 3<br />

11. 4 and 16 12. 3 and 24<br />

Chapter 8 5 Glencoe Geometry

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