103 LearnersLast updated on August 12th, 2025
GCF of 90 and 45
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 to schedule events. In this topic, we will learn about the GCF of 90 and 45.
What is the GCF of 90 and 45?
The greatest common factor of 90 and 45 is 45. 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 90 and 45?
To find the GCF of 90 and 45, a few methods are described below -
- Listing Factors
- Prime Factorization
- Long Division Method / by Euclidean Algorithm
GCF of 90 and 45 by Using Listing of Factors
Steps to find the GCF of 90 and 45 using the listing of factors
Step 1: Firstly, list the factors of each number Factors of 90 = 1, 2, 3, 5, 6, 9, 10, 15, 18, 30, 45, 90. Factors of 45 = 1, 3, 5, 9, 15, 45.
Step 2: Now, identify the common factors of them Common factors of 90 and 45: 1, 3, 5, 9, 15, 45.
Step 3: Choose the largest factor The largest factor that both numbers have is 45. The GCF of 90 and 45 is 45.
GCF of 90 and 45 Using Prime Factorization
To find the GCF of 90 and 45 using the Prime Factorization Method, follow these steps:
Step 1: Find the prime factors of each number
Prime Factors of 90: 90 = 2 x 3 x 3 x 5 = 2 x 3² x 5
Prime Factors of 45: 45 = 3 x 3 x 5 = 3² x 5
Step 2: Now, identify the common prime factors The common prime factors are: 3 x 3 x 5 = 3² x 5
Step 3: Multiply the common prime factors 3² x 5 = 9 x 5 = 45. The Greatest Common Factor of 90 and 45 is 45.
GCF of 90 and 45 Using Division Method or Euclidean Algorithm Method
Find the GCF of 90 and 45 using the division method or Euclidean Algorithm Method. Follow these steps:
Step 1: First, divide the larger number by the smaller number Here, divide 90 by 45 90 ÷ 45 = 2 (quotient), The remainder is calculated as 90 − (45×2) = 0
The remainder is zero, so the divisor will become the GCF. The GCF of 90 and 45 is 45.
Common Mistakes and How to Avoid Them in GCF of 90 and 45
Finding GCF of 90 and 45 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 90, students may mention 7, 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 90 and 45 Examples
Problem 1
A farmer has 90 apples and 45 oranges. He wants to distribute them into equal baskets, with the largest number of fruits in each basket. How many fruits will be in each basket?
We should find the GCF of 90 and 45 GCF of 90 and 45 3² x 5 = 9 x 5 = 45.
There are 45 equal baskets 90 ÷ 45 = 2 45 ÷ 45 = 1
There will be 45 baskets, and each basket gets 2 apples and 1 orange.
Explanation
As the GCF of 90 and 45 is 45, the farmer can make 45 baskets. Now divide 90 and 45 by 45. Each basket gets 2 apples and 1 orange.
Problem 2
A builder has 90 bricks and 45 tiles. He wants to stack them in rows with the same number of items in each row, using the largest possible number of items per row. How many items will be in each row?
GCF of 90 and 45 3² x 5 = 9 x 5 = 45. So each row will have 45 items.
Explanation
There are 90 bricks and 45 tiles. To find the total number of items in each row, we should find the GCF of 90 and 45. There will be 45 items in each row.
Problem 3
A tailor has 90 meters of red fabric and 45 meters of blue fabric. She wants to cut both fabrics 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 90 and 45 The GCF of 90 and 45 3² x 5 = 9 x 5 = 45. The fabric pieces are 45 meters long.
Explanation
For calculating the longest length of the fabric first, we need to calculate the GCF of 90 and 45, which is 45. The length of each piece of fabric will be 45 meters.
Problem 4
A carpenter has two wooden planks, one 90 cm long and the other 45 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 90 and 45 3² x 5 = 9 x 5 = 45. The longest length of each piece is 45 cm.
Explanation
To find the longest length of each piece of the two wooden planks, 90 cm and 45 cm, respectively, we have to find the GCF of 90 and 45, which is 45 cm. The longest length of each piece is 45 cm.
Problem 5
If the GCF of 90 and ‘b’ is 45, and the LCM is 180. Find ‘b’.
The value of ‘b’ is 90.
Explanation
GCF x LCM = product of the numbers
45 × 180 = 90 × b
8100 = 90b
b = 8100 ÷ 90 = 90
FAQs on the Greatest Common Factor of 90 and 45
1.What is the LCM of 90 and 45?
2.Is 90 divisible by 3?
3.What will be the GCF of any two prime numbers?
4.What is the prime factorization of 45?
5.Are 90 and 45 prime numbers?
6.How can children in United States use numbers in everyday life to understand GCF of 90 and 45?
7.What are some fun ways kids in United States can practice GCF of 90 and 45 with numbers?
8.What role do numbers and GCF of 90 and 45 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 90 and 45 skills?
Important Glossaries for GCF of 90 and 45
- Factors: Factors are numbers that divide the target number completely. For example, the factors of 30 are 1, 2, 3, 5, 6, 10, 15, and 30.
- Common Factors: Numbers that are factors of two or more numbers. For example, the common factors of 12 and 18 are 1, 2, 3, and 6.
- 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 45 are 3 and 5.
- Remainder: The value left after division when the number cannot be divided evenly. For example, when 17 is divided by 5, the remainder is 2 and the quotient is 3.
- LCM: The smallest common multiple of two or more numbers is termed LCM. For example, the LCM of 8 and 12 is 24.
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.
