A factor of a whole number divides it evenly, with no remainder. For example, 3 is a factor of 12 because 12 ÷ 3 = 4.
Example: 3 for the number 12
Greatest Common Factor
I can find the greatest common factor (GCF) of two numbers by listing or comparing their factors.
Speaking and writing goal: I can explain how I found the GCF using the words factor, common factor, divisible, and greatest common factor.
What Your Child Is Learning
In this lesson, students practice how to find the greatest common factor (gcf) of two numbers by listing or comparing their factors. They learn to show their thinking with numbers, pictures, words, or a model. The goal is not just getting an answer. Students should be able to explain why the answer makes sense.
Why This Matters
This skill supports everyday problem solving with money, measurements, games, planning, and checking whether an answer is reasonable.
What It May Look Like In Class
Your child may use the interactive lesson, guided notes, examples from the board, partner talk, and short practice problems. They may be asked to solve, draw a model, label important numbers, and explain their reasoning in a sentence.
How You Can Help At Home
You do not need to teach a new method. Ask your child to read the problem out loud, circle the important numbers, and explain what they tried first. Helpful questions include: What do you know? What are you trying to find? Does your answer make sense?
Apoyo para familias en español
Qué está aprendiendo su hijo/a
En esta lección, su hijo/a practica usar números con cuidado y explicar sus pasos. Puede usar dibujos, números, palabras o modelos para mostrar su pensamiento. Lo más importante es que pueda explicar por qué su respuesta tiene sentido.
Por qué es importante
Esta habilidad ayuda con dinero, medidas, juegos, planificación y con revisar si una respuesta es razonable.
Cómo puede ayudar en casa
No necesita ser experto/a en matemáticas. Pídale a su hijo/a que lea el problema en voz alta, marque los números importantes y explique su primer paso. Puede preguntar: ¿Qué sabes? ¿Qué necesitas encontrar? ¿Tu respuesta tiene sentido?
Key Vocabulary
The biggest number that divides two or more numbers evenly.
A number that divides two or more numbers evenly.
A number you can divide evenly, with nothing left over.
Example: 15 is divisible by 3
Writing a number as prime numbers multiplied together. It helps you find the GCF.
Try It Together
Pick one or two problems. Let your child explain the first step before opening the answer.
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Make a factor tree for 36.
Show answer
36 = 2 x 2 x 3 x 3
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List all factors of 24.
Show answer
1, 2, 3, 4, 6, 8, 12, 24
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Is 29 prime or composite? How do you know?
Show answer
Prime; only 1 and 29 divide it evenly.
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What is the greatest common factor of 18 and 30?
Show answer
6