EXAMPLE 1

1. EXAMPLE 1 Modeling Integer Addition Football During a high school football game, your team gained 6 yards on the first play, lost 8 yards on the second play, and gained 11 yards on the third play. Did your team gain the 10 yards needed for a first down?

2. EXAMPLE 1 Modeling Integer Addition To understand the problem above, read and organize the information. First play: 6 means a gain of 6 yards. Second play:– 8 means a loss of 8 yards. Third play:11 means a gain of 11 yards. Start at 0 on a number line. Use arrows to represent gains and losses. Move right to add a positive number and left to add a negative number.

3. EXAMPLE 1 Modeling Integer Addition First play:0 + 6 = 6 Second play: 6 + (–8) = – 2 Third play:–2 + 11 = 9 ANSWER Your team gained only 9 yards during the three plays. It did not gain the 10 yards needed for a first down.

4. for Example 1 GUIDED PRACTICE Find the sum using a number line. 3.– 8 + 10 1. – 4 + (– 4 ) ANSWER ANSWER – 8 2 2.– 6 + 6 4. 5 + (– 9 ) ANSWER ANSWER 0 – 4

5. EXAMPLE 2 Adding Integers Find the sum. a. – 4 + (–7) SOLUTION • Both numbers have the same sign. – 4 + (–7) = – 11 Add |– 4| and |– 7|. Use common sign.

6. EXAMPLE 2 Adding Integers b. – 8 + 3 SOLUTION b.The numbers have different signs, and – 8 has the greater absolute value. – 8 + 3 = – 5 Subtract | 3 | from |– 8|. Use the sign of – 8.

7. EXAMPLE 2 Adding Integers c. – 6 + 9 SOLUTION c.The numbers have different signs, and 9 has the greater absolute value. – 6 + 9 = 3 Subtract |– 6 | from | 9 |. Use the sign of 9.

8. EXAMPLE 1 for Example 2 Adding Integers GUIDED PRACTICE Find the absolute value of each number. Then find the sum. 5. – 10 + (–5) ANSWER 10, 5; –15

9. EXAMPLE 1 for Example 2 Adding Integers GUIDED PRACTICE 6. – 6 + 19 ANSWER 6, 19; 13

10. EXAMPLE 1 for Example 2 Adding Integers GUIDED PRACTICE 7. 8 + (– 15) ANSWER 8, 15; –7

11. EXAMPLE 1 for Example 2 Adding Integers GUIDED PRACTICE 8. 25 + (– 25) ANSWER 25, 25; 0