Adding and Subtracting Integers

Adding and Subtracting Integers

Adding Integers with the Same Sign

When you add integers with the same sign, add the numbers together and keep the sign.

6 + 5 = 11

-4 + -3 = -7

Multiple Choice

8 + 4

• 12

• -12

• 4

• -4

Multiple Choice

-5 + -1 =

• 6

• -6

• 4

• -4

Adding Integers with Different Signs

When adding integers with different signs, subtract the numbers (starting with the number with the largest absolute value, I have highlighted that number in each example below) and keep the sign of the number with the largest absolute value.

9 + -3 = 6

-8 + 1 = -7

5 + -8 = -3

-4 + 6 = 2

Multiple Choice

-6 + 3 =

• 3

• -3

• 9

• -9

Multiple Choice

-5 + 15 =

• 20

• -10

• 10

• -20

Subtracting Integers

When subtracting integers, use the KISS method.

K I (Keep It) S (Switch) S (Switch)

Keep the first number. Switch the subtraction sign to addition. Switch the sign of the second number. Then, follow the rules for adding.

8 - 2 =

Keep the 8, switch - to +, switch 2 to -2.

8 + -2 = 6

(If you are able to do the subtraction without KISS, that is fine, but it works with any numbers and some students find addition easier than subtraction).

More Examples of Subtracting Integers

3 - 9 = (Keep It Switch Switch) 3 + -9 = -6

KISS is especially helpful if you are subtracting a negative number!

5 - (-8) = (Keep It Switch Switch) 5 + 8 = 13

Subtracting a negative is really just adding a positive!!

Multiple Choice

15 - 10 =

• 5

• 25

• -5

• -25

Multiple Choice

6 - 13 =

• 7

• 19

• -19

• -7

Multiple Choice

What is another way of writing

7 - (-3) =

(Remember KISS)

• 3 - 7 =

• 7 + 3 =

• 7 - 3

Multiple Choice

9 - (-8) =

• 1

• -1

• -17

• 17