Adding Integers and Developing Rules

1
Adding Integers and Developing Rules
2

• -9 -6
• Correct answer is -15
• What are you doing with the numbers?
• If both signs are negative how does that affect
  your answer?

3

• -12 7
• Correct answer is -5
• What are you doing with the numbers?
• If the signs are different, how does that affect
  your answer?

• 10 -6
• Correct answer is 4
• What are you doing with the numbers?
• If the signs are different, how does that affect
  your answer?

4
Develop Rules

• If you are adding integers with the same sign,
  what do you do? (Example 1)
• Add the absolute value of the numbers keep the
  sign
• If you are adding integers with different signs,
  what do you do? (Example 2 and 3)
• Subtract the absolute value of the numbers, and
  keep the sign of the greater absolute value.
• Absolute value how far the number is away from
  zero

5
Example 1

• -9 -3
• Adding integers with the same sign
• Add the numbers
• Keep the sign

9 3 12
-12
-9 -3 -12
6
Example 2

• -15 7
• Adding integers with different signs
• Subtract the numbers
• Take the sign of the greater absolute value.

15 7 8
-15 7 -8
-15 has the greater absolute value.
7
Example 2

• 9 -4
• Adding integers with different signs
• Subtract the numbers
• Take the sign of the greater absolute value.

9 4 5
9 -4 5
9 has the greater absolute value.
8
Practice Problems

• -18 -4
• 2. 25 -10
• 3. -13 -5
• 4. -19 6
• -14 14
• 6. -6 -3 7
• 7. -5 8 -6

-22
15
-18
-13
0
-9 7
-2
3 -6
-3
9
Word Problems with Integers

• At 8am the temperature was -6F. At noon, the
  temperature rose 9 degrees. What was the
  temperature at noon?
• -6 9 3F
• The temperature at noon was 3F.
• A submarine is situated 400 feet below sea level.
  If it rises 125 feet, what is its new position?
• -400 125 -275
• The new position of the submarine is 275 feet
  below sea level.