Multiplying Binomials with FOIL
9-12
2
Adding Fractions with Unlike Denominators
Lesson Details
Grade Level
6-8
Duration (minutes)
2
Summary
A Grade 6-8 math lesson teaching students how to add fractions with different denominators by finding the least common denominator (LCD), rewriting each fraction with that denominator, and then adding the numerators, using 1/4 + 1/6 as the worked example.
Student Worksheet: Adding Fractions with Unlike Denominators
Teacher Note: Students can watch the video lesson above and answer the questions. Click the “Teacher Answer Key” dropdown below when you are ready to review the solutions!
Key Concepts:
• Denominators Must Match: You cannot add fractions with different denominators until the pieces are the same size.
• Least Common Denominator (LCD): The LCD is the least common multiple of the denominators — find it by listing multiples of each denominator.
• Converting Fractions: Multiply both the numerator and denominator of each fraction by the same number to rewrite it with the LCD.
• Adding: Once both fractions have the same denominator, add the numerators and keep the denominator the same.
Instructions: Read each question carefully and write your answer in the space provided.
- Question 1: Why can’t you add 1/4 + 1/6 right away?
- Question 2: What is the LCD of 4 and 6, and how do you find it?
- Question 3: Convert 1/4 to a fraction with a denominator of 12. What number did you multiply by, and what is the result?
- Question 4: Convert 1/6 to a fraction with a denominator of 12. What number did you multiply by, and what is the result?
- Question 5: Add the two converted fractions. What is 1/4 + 1/6?
Click to reveal Teacher Answer Key
1. Because the denominators are different, so the pieces are different sizes and can’t be combined directly.
2. The LCD is 12. Multiples of 4 are 4, 8, 12; multiples of 6 are 6, 12 — the first number they share is 12.
3. Multiply by 3 (since 4 × 3 = 12): 1/4 × 3/3 = 3/12.
4. Multiply by 2 (since 6 × 2 = 12): 1/6 × 2/2 = 2/12.
5. 3/12 + 2/12 = 5/12.
Disclaimer: This worksheet was generated with AI assistance based on original video content. It is intended for educational reference only. Teachers are encouraged to review and adjust questions to fit their curriculum standards before classroom use.
🎯 Extension Activity: Add 1/3 + 1/5 by finding the LCD, converting each fraction, and adding the numerators. Show every step, just like the example in the video.