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103 LearnersLast updated on September 18, 2025
GCF of 9 and 30
The GCF is the largest number that can divide two or more numbers without leaving any remainder. GCF is used to share the items equally, to group or arrange items, and schedule events. In this topic, we will learn about the GCF of 9 and 30.
What is the GCF of 9 and 30?
The greatest common factor of 9 and 30 is 3. The largest divisor of two or more numbers is called the GCF of the number. 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 9 and 30?
To find the GCF of 9 and 30, a few methods are described below
- Listing Factors
- Prime Factorization
- Long Division Method / by Euclidean Algorithm
GCF of 9 and 30 by Using Listing of factors
Steps to find the GCF of 9 and 30 using the listing of factors:
Step 1: Firstly, list the factors of each number
Factors of 9 = 1, 3, 9.
Factors of 30 = 1, 2, 3, 5, 6, 10, 15, 30.
Step 2: Now, identify the common factors of them Common factors of 9 and 30: 1, 3.
Step 3: Choose the largest factor The largest factor that both numbers have is 3. The GCF of 9 and 30 is 3.
GCF of 9 and 30 Using Prime Factorization
To find the GCF of 9 and 30 using the Prime Factorization Method, follow these steps:
Step 1: Find the prime factors of each number
Prime Factors of 9: 9 = 3 × 3 = 3²
Prime Factors of 30: 30 = 2 × 3 × 5 = 2 × 3 × 5
Step 2: Now, identify the common prime factors The common prime factor is 3.
Step 3: Multiply the common prime factors The Greatest Common Factor of 9 and 30 is 3.
GCF of 9 and 30 Using Division Method or Euclidean Algorithm Method
Find the GCF of 9 and 30 using the division method or Euclidean Algorithm Method. Follow these steps:
Step 1: First, divide the larger number by the smaller number Here, divide 30 by 9 30 ÷ 9 = 3 (quotient), The remainder is calculated as 30 − (9×3) = 3 The remainder is 3, not zero, so continue the process
Step 2: Now divide the previous divisor (9) by the previous remainder (3)
Divide 9 by 3 9 ÷ 3 = 3 (quotient), remainder = 9 − (3×3) = 0
The remainder is zero, the divisor will become the GCF.
The GCF of 9 and 30 is 3.
Common Mistakes and How to Avoid Them in GCF of 9 and 30
Finding GCF of 9 and 30 looks simple, but students often make mistakes while calculating the GCF. Here are some common mistakes to be avoided by the students.
Mistake 1
Listing Incorrect Factors
Students may sometimes list incorrect factors.
For example, while listing factors of 9, students may mention 2, 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 tells about the 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 that 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 9 and 30 Examples
Problem 1
A florist is arranging 9 red roses and 30 white roses into bouquets. She wants to use the greatest number of roses in each bouquet without any left over. How many roses will be in each bouquet?
We should find the GCF of 9 and 30 GCF of 9 and 30 is 3.
There are 3 roses in each bouquet. 9 ÷ 3 = 3 30 ÷ 3 = 10
There will be 3 bouquets, and each bouquet contains 3 red roses and 10 white roses.
Explanation
As the GCF of 9 and 30 is 3, the florist can make bouquets with 3 roses each.
Now divide 9 and 30 by 3.
Each bouquet contains 3 red roses and 10 white roses.
Problem 2
A band has 9 trumpets and 30 flutes. They want to arrange them in rows with the same number of instruments in each row, using the largest possible number of instruments per row. How many instruments will be in each row?
GCF of 9 and 30 is 3. So each row will have 3 instruments.
Explanation
There are 9 trumpets and 30 flutes.
To find the total number of instruments in each row, we should find the GCF of 9 and 30.
There will be 3 instruments in each row.
Problem 3
A chef has 9 kilograms of flour and 30 kilograms of sugar. He wants to package them into bags of equal weight, using the greatest possible weight for each bag. What should be the weight of each bag?
For calculating the greatest equal weight, we have to calculate the GCF of 9 and 30.
The GCF of 9 and 30 is 3.
Each bag will weigh 3 kilograms.
Explanation
For calculating the greatest weight of each bag, first, we need to calculate the GCF of 9 and 30, which is 3.
The weight of each bag will be 3 kilograms.
Problem 4
A carpenter has two wooden planks, one 9 cm long and the other 30 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 9 and 30 is 3.
The longest length of each piece is 3 cm.
Explanation
To find the longest length of each piece of the two wooden planks, 9 cm and 30 cm, respectively.
We have to find the GCF of 9 and 30, which is 3 cm.
The longest length of each piece is 3 cm.
Problem 5
If the GCF of 9 and ‘b’ is 3, and the LCM is 90, find ‘b’.
The value of ‘b’ is 30.
Explanation
GCF × LCM = product of the numbers
3 × 90 = 9 × b
270 = 9b
b = 270 ÷ 9 = 30
FAQs on the Greatest Common Factor of 9 and 30
1.What is the LCM of 9 and 30?
2.Is 9 divisible by 3?
3.What will be the GCF of any two prime numbers?
4.What is the prime factorization of 30?
5.Are 9 and 30 prime numbers?
Important Glossaries for GCF of 9 and 30
- Factors: Factors are numbers that divide the target number completely. For example, the factors of 15 are 1, 3, 5, and 15.
- Multiple: Multiples are the products we get by multiplying a given number by another. For example, the multiples of 3 are 3, 6, 9, 12, 15, and so on.
- 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 18 are 2 and 3.
- Remainder: The value left after division when the number cannot be divided evenly. For example, when 11 is divided by 4, the remainder is 3 and the quotient is 2.
- LCM: The smallest common multiple of two or more numbers is termed LCM. For example, the LCM of 9 and 30 is 90.
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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.
