Lesson 09: Multiplying Signed Numbers

Page Menu

• Lesson Description
• Learning Objectives
• Topics Covered
• Key Terms
• Lesson Examples
• Practice Problems
• Tips & Common Mistakes
• Summary
• Challenge Problems
• Unit Navigation

Lesson Description

This lesson teaches how to multiply positive and negative numbers, including the rules of signs and visualizations using number lines and examples.

Learning Objectives

• Apply rules for multiplying positive and negative numbers.
• Understand the effect of sign changes in multiplication.
• Use number lines and examples to solve multiplication problems with signed numbers.

Topics Covered

• Rules for multiplying positive and negative numbers
• Multiplying integers
• Visualizing multiplication on a number line
• Common mistakes in signed multiplication

Key Terms

• Positive × Positive: The product is positive.
• Negative × Positive: The product is negative.
• Negative × Negative: The product is positive.

Lesson Examples

Example 1: Multiplying Positive and Negative Numbers

1. Calculate 4 × (-3).
2. Different signs → product is negative.
3. Multiply absolute values: 4 × 3 = 12 → Result = -12.

Example 2: Multiplying Two Negative Numbers

1. Calculate -5 × (-2).
2. Same signs → product is positive.
3. Multiply absolute values: 5 × 2 = 10 → Result = 10.

Practice Problems

1. 3 × (-7) = ?
2. -6 × 4 = ?
3. -2 × (-8) = ?
4. 5 × 0 = ?

Tips & Common Mistakes

• Always check the signs before multiplying.
• Remember: Negative × Negative = Positive.
• Multiplying by zero always gives zero.

Summary

Multiplying signed numbers requires following the rules of signs. Using absolute values and checking signs ensures accurate results in all multiplication problems.

Challenge Problems

1. Calculate -7 × (-6) and explain why the product is positive.
2. Compute 8 × (-5) using a number line.
3. Create three multiplication problems with mixed signs for practice.