Fraction Subtraction Showdown: Mastering Unlike Denominators!

Mathematics Grades 7th Grade 5:00 Video
Print Lesson Plan Watch Video

Lesson Description

Learn how to conquer fraction subtraction by finding common denominators. This lesson plan uses Khan Academy to make fractions fun and easy!

Video Resource

Subtracting fractions with unlike denominators

Khan Academy

Duration: 5:00
Watch on YouTube

Key Concepts

  • Fractions
  • Unlike Denominators
  • Common Denominators
  • Equivalent Fractions
  • Subtraction

Learning Objectives

  • Students will be able to identify fractions with unlike denominators.
  • Students will be able to find the least common denominator (LCD) of two or more fractions.
  • Students will be able to create equivalent fractions with a common denominator.
  • Students will be able to subtract fractions with unlike denominators.

Educator Instructions

  • Introduction (5 mins)
    Begin by reviewing what fractions are and the parts of a fraction (numerator and denominator). Ask students to give examples of fractions they encounter in their daily lives (e.g., pizza slices, time). Briefly discuss equivalent fractions.
  • Video Viewing (10 mins)
    Play the Khan Academy video "Subtracting fractions with unlike denominators." Instruct students to take notes on the key steps involved in subtracting fractions with unlike denominators. Emphasize the importance of finding a common denominator.
  • Guided Practice (15 mins)
    Work through several example problems on the board, demonstrating how to find the least common denominator (LCD) and create equivalent fractions. Involve students by asking them to suggest LCDs and help with the calculations. Start with simpler fractions and gradually increase the difficulty.
  • Independent Practice (15 mins)
    Provide students with a worksheet containing a variety of subtraction problems with unlike denominators. Have them work independently or in pairs to solve the problems. Circulate around the classroom to provide assistance as needed.
  • Wrap-up & Assessment (5 mins)
    Review the key steps for subtracting fractions with unlike denominators. Answer any remaining questions. Administer the multiple-choice and fill-in-the-blank quizzes to assess student understanding.

Interactive Exercises

  • Fraction Match Game
    Create a matching game where students match fractions with unlike denominators to their equivalent fractions with a common denominator.
  • Online Practice
    Use online fraction subtraction practice websites (e.g., Khan Academy) for additional practice and immediate feedback.

Discussion Questions

  • Why is it necessary to have a common denominator when subtracting fractions?
  • What are different strategies for finding the least common denominator (LCD)?
  • How can you check your answer when subtracting fractions?

Skills Developed

  • Problem-solving
  • Critical thinking
  • Procedural fluency
  • Conceptual understanding of fractions

Multiple Choice Questions

Question 1:

What is the first step when subtracting fractions with unlike denominators?

Correct Answer: Find a common denominator.

Question 2:

What is the least common denominator (LCD) of 1/3 and 1/4?

Correct Answer: 12

Question 3:

What is 2/5 - 1/5?

Correct Answer: 1/5

Question 4:

To subtract 1/2 - 1/4, what equivalent fraction can you use for 1/2?

Correct Answer: 2/4

Question 5:

What is 5/6 - 1/3?

Correct Answer: 4/6

Question 6:

When are you allowed to subtract fractions directly?

Correct Answer: When the denominators are the same

Question 7:

Which of the following is an equivalent fraction to 1/2?

Correct Answer: 4/8

Question 8:

What is the LCM of 2 and 5?

Correct Answer: 10

Question 9:

What is 3/4 - 1/8?

Correct Answer: 5/8

Question 10:

What is 1/3 - 1/6?

Correct Answer: 1/6

Fill in the Blank Questions

Question 1:

The bottom number of a fraction is called the ________.

Correct Answer: denominator

Question 2:

To subtract fractions, they must have a _______ denominator.

Correct Answer: common

Question 3:

The smallest multiple that two numbers share is called the Least _______ Multiple (LCM).

Correct Answer: Common

Question 4:

When you change a fraction so it has a bigger denominator, it's called creating an ________ fraction.

Correct Answer: equivalent

Question 5:

1/2 is equivalent to ___/4.

Correct Answer: 2

Question 6:

The top number of a fraction is called the _______.

Correct Answer: numerator

Question 7:

To find a common denominator, you can find the _____ of the original denominators.

Correct Answer: LCM

Question 8:

2/3 - 1/6 = ____/6

Correct Answer: 3

Question 9:

3/5 - 1/10 = ____/10

Correct Answer: 5

Question 10:

The inverse operation to addition is ______.

Correct Answer: subtraction

Educational Standards

7.N.1:[Standard] Read, write, represent, and compare rational numbers, expressed as integers, fractions, and decimals. Explain and apply the concept of absolute value. 7.N.1.2:[Objective] Recognize and generate equivalent representations of rational numbers, including equivalent fractions. 7.N.2.5:[Objective] Model and solve problems using rational numbers involving addition, subtraction, multiplication, division, and positive integer exponents.

Teaching Materials

Download ready-to-use materials for this lesson:

Student Worksheet Classroom Slides Assessment Quiz
Add to Google Classroom

User Actions

Sign in to save this lesson plan to your favorites.

Sign In

Share This Lesson

Related Lesson Plans