GCF – Greatest Common Factor
Concept
When looking at all the factors of two or more numbers, some factors are the same (or common). The largest of these common factors is the greatest common factor (GCF).
Rules
To find the greatest common factor of two numbers:
1. List all the factors of each number.
2. Find the greatest factor they have in common
Example
What is the greatest common factor of 42 and 56?
Solution
To find the greatest common factor of 42 and 56:
1. List all the factors of each number:
Factors of 42: 1, 2, 3, 6, 7, 14, 21, 42
Factors of 56: 1, 2, 4, 7, 8, 14, 28, 56
2. Find the greatest factor they have in common.
Greatest Common Factor: 14
Practice Greatest Common Factor (GCF)
Practice Problem 1
What is the greatest common factor of 40 and 48?
Factors of 40: 1, 2, 4, 5, 8, 10, 20, 40
Factors of 48: 1, 2, 3, 4, 6, 8, 12, 16, 24, 48
Practice Problem 2
Find the greatest common factor of 16 and 32
Fill in the missing numbers.
Practice Problem 3
Find the greatest common factor of 20, 24 and 36
Fill in the missing numbers.
Practice Problem 4
What is the greatest common factor of 16, 22 and 36 ?
Multiple is a number that can be divided by another number a certain number of times without a remainder.
Factor is one of two or more numbers that divides a given number without a remainder.
Greatest Common Factor (GCF) – is the largest positive integer that divides evenly into all numbers with zero remainders.
Pre-requisite Skills
Identify Factors
Identify Multiples