Operations with Integers

Review of Operations with Integers

by Mrs. Annett

​Adding & Subtracting Integers

• ​You might have the "rules" memorized already, in which case, great!!! If not, here are a few scenarios to help you make sense of these problems

  • You can think of these in terms of money - you have money (positive) or you owe money (negative)

    • ​-5 + 12 - If I owe $5 to a friend, but I have $12, how much do I have in all?

    • What would this mean? ​-7 + (-3)

    • ​This? 20 - 40

Multiple Choice

5 - 10

• 5

• 15

• -5

• -15

Multiple Choice

-2 + (-9)

• -11

• -7

• 11

• 7

Multiple Choice

45 + (-100)

• 65

• -55

• 45

• -145

Subtracting a Negative - Why do we add?

• I like to remember SAME, SUM and DIFFERENT, DIFFERENCE:

  • if they have the SAME SIGN, you add the values and keep the sign (positive + positive = positive, negative + negative, or negative - positive = negative)

  • ​if they have DIFFERENT SIGNS, you subtract the values and keep the sign of the greater value

Multiple Choice

6 - (-8)

• 2

• -2

• -14

• 14

Multiple Choice

-3 - (-7)

• 4

• -4

• -10

• 10

Quick Review of the "rules"

• ​You might have memorized that minus a negative turns into a plus...for instance 5 - (-5) can be rewritten as 5 + 5...but have you ever seen a scenario explaining why???

  • ​With money, we can think of this as taking away debt, which is basically the same as earning money.

    • ​20 - (-10)

  • ​If that's confusing to you, maybe seeing this demonstration of a hot air balloon will help you make sense of minus negative problems

    https://www.geogebra.org/m/CSb4Zq8P

    • ​-2 - (-2)

Multiple Choice

12 - 20

• -8

• 8

• 32

• -32

Multiple Choice

-9 + (-8)

• -1

• 1

• -17

• 17

Multiple Choice

-20 - 10

• -10

• 10

• 30

• -30

Multiplying & Dividing Integers

• ​You can memorize these rules pretty easily, but until you have it mastered, feel free to use the triangle as a tool!

  • ​-2 * 4

  • ​-18 / -6

Multiple Choice

-2 * -5

• 10

• -10

• 7

• -7

Multiple Choice

-3 * 7

• 10

• -10

• 21

• -21

Multiple Choice

4 * -4

• -16

• 16

• 0

• -1

Multiple Choice

48 / -8

• -6

• 6

• 40

• -40

Multiple Choice

-10 / -5

• -2

• 2

• -5

• 5