1. Addition, Subtraction, Multiplication, and Division of Integers
Lesson 11
Addition, Subtraction, Multiplication, and Division of Integers

2. Rules for Adding Integers
When the signs are the same, keep the sign and add.
When the signs are different, take the sign of the number with the higher absolute value and subtract.

3. Example 1
6 + (-14) + (-10) + 30 =
Strategy: Follow the rules for adding integers.
Step 1: Add the positive integers.
= 36
Step 2: Add the negative integers.
(-14) + (-10) = (-24)

4. Step 3: Add the solutions from Steps 1 and 2.
36 + (-24) = 12

5. Solution
The answer is 12.

6. Rules for Subtracting Integers
Rewrite the subtraction problem as an addition problem:
Change the minus to a plus.
Change the sign of the number to be subtracted (the second number). If the second number is positive, make it negative; if the second number is negative, make it positive.
Solve using the rules for addition.

7. Example 2 Subtract: 16 – (-13) =
Strategy: Rewrite the problem as an addition problem.
Step 1: Rewrite the problem. =
Step 2: Add.
= 29

8. Solution
The answer is 29.

9. Rules for Multiplying Integers
If the signs are alike, the answer is positive.
If the signs are different, the answer is negative.

10. Example 3
(-25) x (-8) x (-2) =
Strategy: Follow the rules for multiplying integers.
Step 1: Multiply the numbers.
25 x 8 x 2 = 400
Step 2: Determine the sign of the answer.
(-) x (-) = (+); (+) x (-) = (-)
The sign of the answer is negative.
-400

11. Solution
The product is -400.

12. Rules for Dividing Integers
If the signs are alike, the answer is positive.
If the signs are different, the answer is negative.

13. Example 4 Divide: (-20) / (5) =
Strategy: Follow the rules for dividing integers.
Step 1: Divide the numbers.
20 / 5 = 4
Step 2: Determine the sign of the answer.
The signs are different; negative. -4

14. Solution
The quotient is -4.