Page 41 - Basic College Mathematics with Early Integers

18 C HAPTE R 1 I THE WHOLE NUMBERS

Associative Property of Addition

Changing the grouping of addends does not change their sum. For example,
3 +(5+7)=3+12=15 and (3+5)+7=8+7=15

The commutative and associative properties tell us that we can add whole numbers
using any order and grouping that we want.
When adding several numbers, it is often helpful to look for two or three
numbers whose sum is 10, 20, and so on. Why? Adding multiples of 10 such as
10 and 20 is easier.

PRACTICE 3 Example 3 Add: 13 + 2 + 7 + 8 + 9
Add: 11 + 7 + 8 + 9 + 13
Solution: 13+2+7+8+9=39

20+10+9

39

Work Practice 3

Feel free to use the process of Example 3 anytime when adding.

PRACTICE 4 Example 4 Add: 1647 + 246 + 32 + 85
Add: 19 + 5042 + 638 + 526 1 2 2
Solution: 1647
246
32
+ 85
2010

Work Practice 4

Objective Finding the Perimeter of a Polygon

In geometry addition is used to find the perimeter of a polygon. A polygon can be
described as a flat figure formed by line segments connected at their ends. (For
more review, see Appendix A.3.) Geometric figures such as triangles, squares, and
rectangles are called polygons.

Copyright 2012 Pearson Education, Inc.

Triangle Square Rectangle

Answers The perimeter of a polygon is the distance around the polygon.This means that
3. 48 4. 6225 the perimeter of a polygon is the sum of the lengths of its sides.