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Lesson 1-2: Integer Multiplication & Division

Scenario: Banking & Temperature - Learn multiplication and division rules through financial and temperature scenarios!

Duration: 55-70 minutesScenario: Banking & Temperature

Learning Objectives

  • Apply sign rules for multiplication and division of integers
  • Solve banking and financial problems using integer operations
  • Calculate rates and averages involving negative numbers
  • Understand patterns in multiple negative number operations

Banking Scenario

The Problem

A bank account has a monthly overdraft fee of $150. If this fee is charged for 6 months, what is the total change in the account balance?

Calculation: -150 × 6 = -900 dollars

The account balance decreases by $900 over 6 months.

Sign Rules for Multiplication

Same Signs → Positive

Positive × Positive = Positive
Negative × Negative = Positive

Examples: 3 × 4 = 12, (-3) × (-4) = 12

Different Signs → Negative

Positive × Negative = Negative
Negative × Positive = Negative

Examples: 3 × (-4) = -12, (-3) × 4 = -12

Temperature & Rate Calculations

Temperature Drop Problem

Over 5 days, the temperature drops by 10°C. What is the average daily temperature change?

Calculation: -10 ÷ 5 = -2°C per day

The temperature drops an average of 2°C each day.

Sign Rules for Division

Same Signs → Positive

Positive ÷ Positive = Positive
Negative ÷ Negative = Positive

Examples: 12 ÷ 3 = 4, (-12) ÷ (-3) = 4

Different Signs → Negative

Positive ÷ Negative = Negative
Negative ÷ Positive = Negative

Examples: 12 ÷ (-3) = -4, (-12) ÷ 3 = -4

Multiple Negative Numbers

The Pattern

Key Rule: Count the number of negative signs in the multiplication.

  • • Even number of negatives → Positive result
  • • Odd number of negatives → Negative result

Examples

Even Negatives (Positive Result)

(-3) × (-4) × (-2) × (-1) = 24
4 negatives → positive

Odd Negatives (Negative Result)

(-3) × (-4) × (-2) = -24
3 negatives → negative

Practice Problems

Problem 1

Calculate: (-8) × 5 = ?

Your solution:

Problem 2

Calculate: (-24) ÷ (-6) = ?

Your solution:

Problem 3: Multiple Negatives

Calculate: (-2) × (-3) × (-4) = ?

Your solution:

Step 1: (-2) × (-3) =
Step 2: 6 × (-4) =

Problem 4: Real-World Application

A stock loses $3 per day for 7 days. What is the total change in value?

Your calculation: