GCF, LCM, Factor Trees & the Venn Diagram Method
Multiples & Factors Anchor Chart
GCF & LCM — Factor Trees & Venn Diagram
GCF & LCM — The List Method
Understanding multiples and factors unlocks two of the most useful skills in upper elementary math — simplifying fractions and finding common denominators. This page covers both concepts from the ground up, then shows two powerful methods for finding the Greatest Common Factor (GCF) and Least Common Multiple (LCM): the factor tree with Venn diagram, and the list method.
Multiples of a number are made by multiplying that number by any whole number. Every number has an infinite number of multiples — they go on forever!
Factors are the numbers you multiply together to get a number. Every number has a fixed number of factors — you can list them all!
Choose a number and watch its multiples light up in the grid below!
Type any number and find all of its factors instantly!
A factor tree breaks a number down into its prime factors. Click through each step to watch the tree grow!
Factor Tree of 18
Factor Tree of 24
Using the prime factorizations from the factor trees above: 18 = 2 × 3 × 3 and 24 = 2 × 2 × 2 × 3
Click each prime factor in the bank below, then click where it belongs in the Venn diagram!
The list method works great for smaller numbers. Write out the factors or multiples, then circle the answer!
List ALL factors of each number. Circle the greatest one they share.
List MULTIPLES of each number. Circle the smallest one they share.
Hot dogs come in packages of 10. Hot dog buns come in packages of 8. How many packages of each would you need to have the same number of hot dogs and buns?
Choose a set and check your answers!
Find the 5th multiple of each number.
How many factors does each number have?
Find the Greatest Common Factor of each pair.
Find the Least Common Multiple of each pair.
Students take turns choosing numbers from a grid. Their score is the sum of all factors of that number not yet claimed. The player with the highest score wins. This builds factor fluency in a competitive, engaging way.
Use the hot dog and bun problem as an introduction. Then have students find their own real-world LCM problems — items that come in different-sized packages that they'd want equal amounts of.
Immediately connect GCF to simplifying fractions and LCM to finding common denominators. Students understand the purpose better when they see how these skills are used in the very next lesson.
Have students use three colors — one for each section of the Venn diagram. The overlap color reminds them that shared factors go in the GCF calculation, while all colors together form the LCM.
The downloadable foldables work beautifully in interactive notebooks. The two-pocket design for Multiples and Factors lets students store their own examples, making it a personalized reference tool.
Teach divisibility rules for 2, 3, and 5 alongside factor trees. Students who know that a number is divisible by 3 if its digits sum to a multiple of 3 will build factor trees much more efficiently.
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