How do you multiply 4 ∙ -3, and how does that relate to 4 ∙ 3?

In this lesson you will learn to multiply positive and

negative integers by using a number line.

Let’s ReviewLet’s Review

What’s an integer?Integers include positive and negative

whole numbers as well as 0. ...-3, -2, -1, 0, 1, 2, 3 ...

Non-Examples: -3.1 0.45 -8.6 2

Let’s ReviewLet’s Review

What’s multiplication?Multiplication is the process of scaling one

number by another.3 ∙ 4 = 12

factor factor productMultiplication Symbols

3 × 4 3 ∙ 4 3(4) 3n

Let’s ReviewLet’s Review

8888

3030

What’s the commutative propertyof multiplication

The order in which two numbers are multiplied does not matter.

6 ∙ 5 =5 ∙ 6 =

14 14

7 ∙ 2 =2 ∙ 7 =

11 ∙ 8 =8 ∙ 11 =

6 ∙ 5 = 5 ∙ 6 7 ∙ 2 = 2 ∙ 7 11 ∙ 8 = 8 ∙ 11

Let’s ReviewA Common Mistake

Multiplying without accounting for the signs of the two factors.

-9 ∙ 4 = 36 5 ∙ -3 = 15--

Let’s ReviewCore Lesson

-1-7

-1 · 7

7 · -1 7

-7

-7

-7

Let’s ReviewCore Lesson

-3 · 4 -3

-12

4 · -3 4-12

-12

12

-12

In this lesson you learned to multiply positive and

negative integers by using a number line.

Let’s ReviewGuided Practice

Multiply -5 and 8.

Let’s ReviewGuided Practice

Simplify: 9 ∙ -6.

Let’s ReviewExtension Activities

Solve -6 ∙ 4 and 4 ∙ -6 on two different number lines.

What do you notice? Write a few sentences to explain what happened.

Let’s ReviewExtension Activities

Solve:-1 ∙ 3 =-2 ∙ 3 =-3 ∙ 3 =-4 ∙ 3 =-5 ∙ 3 =

What pattern do you see?

Let’s ReviewExtension ActivitiesCompare and contrast the following problem sets: Problem Set 1 Problem Set 2

6 x 4 = 6 x 4 =6 x 3 = 6 x 3 =6 x 2 = 6 x 2 =6 x 1 = 6 x 1 =6 x 0 = 6 x 0 =6 x -1 = -6 x 1 =6 x -2 = -6 x 2 =6 x -3 = -6 x 3 =6 x -4 = -6 x 4 =

Let’s ReviewQuick Quiz

1. Simplify 12 ∙ -4.

2. Multiply -2 and 7.