102 LearnersLast updated on August 5th, 2025
GCF of 28 and 49
The GCF is the largest number that can divide two or more numbers without leaving any remainder. GCF is used to share items equally, to group or arrange items, and schedule events. In this topic, we will learn about the GCF of 28 and 49.
What is the GCF of 28 and 49?
The greatest common factor of 28 and 49 is 7. The largest divisor of two or more numbers is called the GCF of the numbers. If two numbers are co-prime, they have no common factors other than 1, so their GCF is 1. The GCF of two numbers cannot be negative because divisors are always positive.
How to find the GCF of 28 and 49?
To find the GCF of 28 and 49, a few methods are described below:
- Listing Factors
- Prime Factorization
- Long Division Method / Euclidean Algorithm
GCF of 28 and 49 by Using Listing of Factors
Steps to find the GCF of 28 and 49 using the listing of factors:
Step 1: Firstly, list the factors of each number.
Factors of 28 = 1, 2, 4, 7, 14, 28.
Factors of 49 = 1, 7, 49.
Step 2: Now, identify the common factors of them.
Common factors of 28 and 49: 1, 7.
Step 3: Choose the largest factor.
The largest factor that both numbers have is 7.
The GCF of 28 and 49 is 7.
GCF of 28 and 49 Using Prime Factorization
To find the GCF of 28 and 49 using the Prime Factorization Method, follow these steps:
Step 1: Find the prime factors of each number.
Prime Factors of 28: 28 = 2 x 2 x 7 = 2² x 7
Prime Factors of 49: 49 = 7 x 7 = 7²
Step 2: Now, identify the common prime factors.
The common prime factor is: 7
Step 3: Multiply the common prime factor. 7 = 7.
The Greatest Common Factor of 28 and 49 is 7.
GCF of 28 and 49 Using Division Method or Euclidean Algorithm Method
Find the GCF of 28 and 49 using the division method or Euclidean Algorithm Method. Follow these steps:
Step 1: First, divide the larger number by the smaller number.
Here, divide 49 by 28. 49 ÷ 28 = 1 (quotient),
The remainder is calculated as 49 - (28×1) = 21.
The remainder is 21, not zero, so continue the process.
Step 2: Now divide the previous divisor (28) by the previous remainder (21).
Divide 28 by 21. 28 ÷ 21 = 1 (quotient), remainder = 28 - (21×1) = 7.
Step 3: Now divide 21 by the remainder (7). 21 ÷ 7 = 3 (quotient), remainder = 21 - (7×3) = 0.
The remainder is zero, the divisor becomes the GCF.
The GCF of 28 and 49 is 7.
Common Mistakes and How to Avoid Them in GCF of 28 and 49
Finding the GCF of 28 and 49 looks simple, but students often make mistakes while calculating the GCF. Here are some common mistakes to be avoided by students.
Mistake 1
Listing Incorrect Factors
Students may sometimes list incorrect factors.
For example, while listing factors of 28, students may mention 10, which is incorrect. To avoid this, students should carefully divide the number and list the factors correctly.
Mistake 2
Choosing the Wrong Common Factor
Students may sometimes select the smallest common factor instead of the largest one. To avoid this confusion, students should list all the common factors and find the greatest one.
Mistake 3
Forgetting to Include 1 as a Factor
Sometimes students may forget 1 as a common factor of the numbers. However, it does not affect the GCF, but it shows an incomplete understanding of the factors. Students should include 1 as a factor.
Mistake 4
Using Multiples Instead of Factors
Students confuse between factors and multiples. In that confusion, sometimes they may write multiples instead of factors. To avoid this confusion, students should know the definitions of multiples and factors clearly.
Mistake 5
Assuming GCF is Always an Even Number
Students may assume that the GCF of two numbers will always be an even number. But it's not true; a GCF can also be an odd number. To avoid this, students should focus on common factors rather than focusing on even and odd numbers.
Greatest Common Factor of 28 and 49 Examples
Problem 1
A teacher has 28 apples and 49 oranges. She wants to group them into equal sets, with the largest number of items in each group. How many items will be in each group?
We should find the GCF of 28 and 49. GCF of 28 and 49 is 7.
There are 7 equal groups. 28 ÷ 7 = 4 49 ÷ 7 = 7
There will be 7 groups, and each group gets 4 apples and 7 oranges.
Explanation
As the GCF of 28 and 49 is 7, the teacher can make 7 groups.
Now divide 28 and 49 by 7.
Each group gets 4 apples and 7 oranges.
Problem 2
A school has 28 red chairs and 49 blue chairs. They want to arrange them in rows with the same number of chairs in each row, using the largest possible number of chairs per row. How many chairs will be in each row?
GCF of 28 and 49 is 7.
So each row will have 7 chairs.
Explanation
There are 28 red and 49 blue chairs. To find the total number of chairs in each row, we should find the GCF of 28 and 49. There will be 7 chairs in each row.
Problem 3
A tailor has 28 meters of red ribbon and 49 meters of blue ribbon. She wants to cut both ribbons into pieces of equal length, using the longest possible length. What should be the length of each piece?
For calculating the longest equal length, we have to calculate the GCF of 28 and 49. The GCF of 28 and 49 is 7. The ribbon is 7 meters long.
Explanation
For calculating the longest length of the ribbon, first, we need to calculate the GCF of 28 and 49, which is 7.
The length of each piece of the ribbon will be 7 meters.
Problem 4
A carpenter has two wooden planks, one 28 cm long and the other 49 cm long. He wants to cut them into the longest possible equal pieces, without any wood left over. What should be the length of each piece?
The carpenter needs the longest piece of wood. GCF of 28 and 49 is 7.
The longest length of each piece is 7 cm.
Explanation
To find the longest length of each piece of the two wooden planks, 28 cm and 49 cm, respectively, we have to find the GCF of 28 and 49, which is 7 cm. The longest length of each piece is 7 cm.
Problem 5
If the GCF of 28 and ‘a’ is 7, and the LCM is 196. Find ‘a’.
The value of ‘a’ is 49.
Explanation
GCF x LCM = product of the numbers 7 × 196 = 28 × a
1372 = 28a
a = 1372 ÷ 28 = 49
FAQs on the Greatest Common Factor of 28 and 49
1.What is the LCM of 28 and 49?
2.Is 28 divisible by 2?
3.What will be the GCF of any two prime numbers?
4.What is the prime factorization of 49?
5.Are 28 and 49 prime numbers?
6.How can children in United States use numbers in everyday life to understand GCF of 28 and 49?
7.What are some fun ways kids in United States can practice GCF of 28 and 49 with numbers?
8.What role do numbers and GCF of 28 and 49 play in helping children in United States develop problem-solving skills?
9.How can families in United States create number-rich environments to improve GCF of 28 and 49 skills?
Important Glossaries for GCF of 28 and 49
- Factors: Factors are numbers that divide the target number completely. For example, the factors of 14 are 1, 2, 7, and 14.
- Prime Factors: These are the factors of a number that are prime numbers and divide the given number completely. For example, the prime factors of 28 are 2 and 7.
- Remainder: The value left after division when the number cannot be divided evenly. For example, when 10 is divided by 3, the remainder is 1 and the quotient is 3.
- LCM: The smallest common multiple of two or more numbers is termed LCM. For example, the LCM of 28 and 49 is 196.
- GCF: The largest factor that commonly divides two or more numbers. For example, the GCF of 28 and 49 is 7, as it is their largest common factor that divides the numbers completely.
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Hiralee Lalitkumar Makwana
About the Author
Hiralee Lalitkumar Makwana has almost two years of teaching experience. She is a number ninja as she loves numbers. Her interest in numbers can be seen in the way she cracks math puzzles and hidden patterns.
Fun Fact
: She loves to read number jokes and games.
