Finding the Biggest Buddies: Understanding Greatest Common Factor (GCF)

Mathematics Grades 4th Grade 11:49 Video
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Lesson Description

Learn how to find the Greatest Common Factor (GCF) of two numbers. This helps us simplify fractions later on!

Video Resource

Finding the Greatest Common Factor

Math and Science

Duration: 11:49
Watch on YouTube

Key Concepts

  • Factors
  • Greatest Common Factor (GCF)
  • Listing Factors to Find GCF

Learning Objectives

  • Students will be able to define factors of a number.
  • Students will be able to define the Greatest Common Factor (GCF).
  • Students will be able to find the GCF of two numbers by listing their factors.

Educator Instructions

  • Introduction (5 mins)
    Begin by asking students if they know what a 'factor' is. Review the definition of a factor: A number that divides evenly into another number. Then, introduce the concept of the 'Greatest Common Factor' as the largest factor that two numbers share. Explain that this skill will be useful when they work with fractions.
  • Video Viewing (10 mins)
    Play the YouTube video 'Finding the Greatest Common Factor.' Instruct students to pay attention to how the instructor lists the factors of each number and then identifies the greatest common factor.
  • Guided Practice (15 mins)
    Work through the examples from the video again, but pause after each step and ask students questions to check their understanding. For example, after listing the factors of 9, ask, 'Why isn't 2 a factor of 9?' Then, work through a few new examples together on the board, such as finding the GCF of 12 and 15, or 8 and 20. Have students actively participate by suggesting factors.
  • Independent Practice (15 mins)
    Provide students with a worksheet containing problems similar to those in the video. Have them work individually or in pairs to find the GCF of different pairs of numbers. Circulate to offer assistance and answer questions.
  • Wrap-up (5 mins)
    Review the key concepts of factors and GCF. Ask students to explain in their own words how to find the GCF of two numbers. Preview the importance of GCF in simplifying fractions.

Interactive Exercises

  • Factor Rainbows
    Students create 'factor rainbows' for different numbers. They write the number at the top, then draw an arch connecting pairs of factors (e.g., for 12: 1 and 12, 2 and 6, 3 and 4).
  • GCF Scavenger Hunt
    Prepare cards with pairs of numbers. Hide the cards around the classroom. Students find the cards, calculate the GCF for each pair, and write their answers on a recording sheet.

Discussion Questions

  • What is a factor?
  • What does 'Greatest Common Factor' mean?
  • Why is finding the GCF important for working with fractions?

Skills Developed

  • Identifying Factors
  • Problem-Solving
  • Applying Mathematical Concepts

Multiple Choice Questions

Question 1:

What is a factor of a number?

Correct Answer: A number that divides evenly into the number

Question 2:

What does GCF stand for?

Correct Answer: Greatest Common Factor

Question 3:

What is the GCF of 6 and 9?

Correct Answer: 3

Question 4:

Which of these is NOT a factor of 12?

Correct Answer: 5

Question 5:

To find the GCF, you need to find the ________ factor that two numbers share.

Correct Answer: Largest

Question 6:

What are the factors of 8?

Correct Answer: 1, 2, 4, 8

Question 7:

What are the factors of 15?

Correct Answer: 1, 3, 5, 15

Question 8:

What is the GCF of 4 and 10?

Correct Answer: 2

Question 9:

Why is it important to know how to find the GCF?

Correct Answer: To make fractions simpler

Question 10:

Which number is a factor of EVERY number?

Correct Answer: 1

Fill in the Blank Questions

Question 1:

A ________ is a number that divides evenly into another number.

Correct Answer: factor

Question 2:

GCF stands for Greatest ________ ________.

Correct Answer: Common Factor

Question 3:

The GCF of 8 and 12 is ________.

Correct Answer: 4

Question 4:

One way to find the GCF is to list all the ________ of each number.

Correct Answer: factors

Question 5:

The factors of 10 are 1, 2, 5, and ________.

Correct Answer: 10

Question 6:

The largest factor that two numbers share is called the ________.

Correct Answer: GCF

Question 7:

Knowing the GCF will help you ________ fractions later.

Correct Answer: simplify

Question 8:

The GCF of 3 and 6 is ________.

Correct Answer: 3

Question 9:

The only factors of 7 are 1 and ________.

Correct Answer: 7

Question 10:

When finding the GCF, look for the ________ common factor.

Correct Answer: greatest

Educational Standards

4.N.2.1:Demonstrate fluency with multiplication and division facts with factors up to 12. 4.N.2.5:Use strategies and algorithms (e.g., mental strategies, standard algorithms, partial quotients, repeated subtraction, the commutative, associative, and distributive properties) based on knowledge of place value, equality, and properties of operations to divide a 3-digit dividend by a 1-digit whole number divisor, with and without remainders.

Teaching Materials

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