Multiplying Integers

Concept 7

Things you need to know…

• A “negative” sign and a “minus” sign mean the same thing

• A “negative” sign and a “minus” sign mean

“change direction”• Always assume your moving in a positive

direction unless you are told to “change direction”

Example: 8

A positive 8 means go forward eight

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10

Example: -8

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10

A “negative” 8 means “change direction” andgo eight

How to Multiply Integers

Using colored beans

Things you need to know

• White means a positive answer• Shaded means a negative answer• To “change direction” simply flip the bean• Always assume you are moving in a

positive direction until you are told to “change direction”

3 x 4

3 x 4

3 x 4

3 x 4

12

-3 x 4

-3 x 4

-3 x 4

-3 x 4

-3 x 4

-12

3 x -4

3 x -4

3 x -4

3 x -4

-12

-3 x -4

-3 x -4

-3 x -4

-3 x -4

-3 x -4

-12

-3 x -4

12

Fast Way

An even number of negative signsin a problem means the solution is positive

An odd number of negative signs in a problem means the solution is negative

7 x -3

Fast Way

An even number of negative signsin a problem means the solution is positive

An odd number of negative signs in a problem means the solution is negative

7 x -3

This problem has one negativeOne is an odd number Therefore, the solution is negativeNow, just multiply the numbers!

Fast Way

An even number of negative signsin a problem means the solution is positive

An odd number of negative signs in a problem means the solution is negative

7 x -3

This problem has one negativeOne is an odd number Therefore, the solution is negativeNow, just multiply the numbers!

-21

Fast Way

An even number of negative signsin a problem means the solution is positive

An odd number of negative signs in a problem means the solution is negative

-4 x -5

Fast Way

An even number of negative signsin a problem means the solution is positive

An odd number of negative signs in a problem means the solution is negative

-4 x -5

This problem has two negativesTwo is an even number Therefore, the solution is positiveNow, just multiply the numbers!

Fast Way

An even number of negative signsin a problem means the solution is positive

An odd number of negative signs in a problem means the solution is negative

-4 x -5

This problem has two negativesTwo is an even number Therefore, the solution is positiveNow, just multiply the numbers!

20

Fast Way

An even number of negative signsin a problem means the solution is positive

An odd number of negative signs in a problem means the solution is negative

-2 x -3 x -1

Fast Way

An even number of negative signsin a problem means the solution is positive

An odd number of negative signs in a problem means the solution is negative

-2 x -3 x -1

This problem has three negativesThree is an odd number Therefore, the solution is negativeNow, just multiply the numbers!

Fast Way

An even number of negative signsin a problem means the solution is positive

An odd number of negative signs in a problem means the solution is negative

-2 x -3 x -1

This problem has three negativesThree is an odd number Therefore, the solution is negativeNow, just multiply the numbers!

-6