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Lesson 2-3: Complex Fractions

Scenario: Speed Calculations - Calculate rates using complex fractions!

Duration: 60-75 minutesScenario: Speed Calculations

Learning Objectives

  • Understand what complex fractions are and how to simplify them
  • Apply the rule: Complex Fraction = Numerator ÷ Denominator
  • Solve rate and speed problems using complex fractions
  • Perform unit analysis and verify solutions

Speed Calculation Problem

Walking Speed Scenario

If you walk ⅔ kilometers in ¾ hours, what is your walking speed in kilometers per hour?

Problem: Speed = Distance ÷ Time = (⅔) ÷ (¾)

Step-by-Step Solution

Step 1: Write as a complex fraction

(⅔) ÷ (¾) = (⅔)/(¾)

Step 2: Apply the rule: Complex Fraction = Numerator ÷ Denominator

(⅔)/(¾) = ⅔ ÷ ¾

Step 3: Multiply by the reciprocal

⅔ ÷ ¾ = ⅔ × 4/3 = (2×4)/(3×3) = 8/9

Step 4: Interpret the result

Speed = 8/9 kilometers per hour ≈ 0.89 km/h

Answer: Your walking speed is 8/9 kilometers per hour.

Understanding Complex Fractions

What are Complex Fractions?

A complex fraction is a fraction where the numerator, denominator, or both contain fractions.

Examples

(⅔)/(¾) - fraction over fraction

2/(½) - whole number over fraction

(1½)/3 - mixed number over whole number

Simplification Rule

Complex Fraction = Numerator ÷ Denominator

Then use "Keep, Change, Flip" for division

More Examples

Example 1: Drinking Rate

If you drink ½ cup per minute, how many cups do you drink in ¼ hour?

Solution: ¼ hour = 15 minutes
Cups = ½ cup/min × 15 min = 7.5 cups

Example 2: Complex Fraction

Simplify: (3/5)/(6/7)

Solution: (3/5)/(6/7) = 3/5 ÷ 6/7 = 3/5 × 7/6 = 21/30 = 7/10

Example 3: Decimal Complex Fraction

Simplify: (1.2)/(3/4)

Solution: (1.2)/(3/4) = 1.2 ÷ 3/4 = 1.2 × 4/3 = 4.8/3 = 1.6

Practice Problems

Problem 1

A car travels 1½ miles in ⅔ hours. What is the car's speed in miles per hour?

Your solution:

Problem 2

Simplify: (2/3)/(4/5)

Your solution: