Last updated on August 5th, 2025
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 4 and 20.
The greatest common factor of 4 and 20 is 4. 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.
To find the GCF of 4 and 20, a few methods are described below:
Steps to find the GCF of 4 and 20 using the listing of factors:
Step 1: Firstly, list the factors of each number:
Factors of 4 = 1, 2, 4.
Factors of 20 = 1, 2, 4, 5, 10, 20.
Step 2: Now, identify the common factors of them Common factors of 4 and 20: 1, 2, 4.
Step 3: Choose the largest factor The largest factor that both numbers have is 4.
The GCF of 4 and 20 is 4.
To find the GCF of 4 and 20 using the Prime Factorization Method, follow these steps:
Step 1: Find the prime factors of each number:
Prime Factors of 4: 4 = 2 x 2 = 2²
Prime Factors of 20: 20 = 2 x 2 x 5 = 2² x 5
Step 2: Now, identify the common prime factors The common prime factors are: 2 x 2 = 2²
Step 3: Multiply the common prime factors 2² = 4.
The Greatest Common Factor of 4 and 20 is 4.
Find the GCF of 4 and 20 using the division method or Euclidean Algorithm Method. Follow these steps:
Step 1: First, divide the larger number by the smaller number Here, divide 20 by 4 20 ÷ 4 = 5 (quotient).
The remainder is calculated as 20 − (4×5) = 0
The remainder is zero, the divisor will become the GCF.
The GCF of 4 and 20 is 4.
Finding the GCF of 4 and 20 looks simple, but students often make mistakes while calculating the GCF. Here are some common mistakes to be avoided by the students.
A gardener has 4 flower pots and 20 seed packets. She wants to arrange them into equal groups with the largest number of items in each group. How many items will be in each group?
We should find the GCF of 4 and 20 GCF of 4 and 20 2² = 4.
There are 4 equal groups
4 ÷ 4 = 1
20 ÷ 4 = 5
There will be 4 groups, and each group gets 1 flower pot and 5 seed packets.
As the GCF of 4 and 20 is 4, the gardener can make 4 groups.
Now divide 4 and 20 by 4.
Each group gets 1 flower pot and 5 seed packets.
A baker has 4 chocolate bars and 20 cookies. They want to arrange them in trays with the same number of items in each tray, using the largest possible number of items per tray. How many items will be in each tray?
GCF of 4 and 20 2² = 4. So each tray will have 4 items.
There are 4 chocolate bars and 20 cookies.
To find the total number of items in each tray, we should find the GCF of 4 and 20.
There will be 4 items in each tray.
A tailor has 4 meters of red fabric and 20 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 4 and 20
The GCF of 4 and 20 2² = 4.
The fabric is 4 meters long.
For calculating the longest length of the fabric first, we need to calculate the GCF of 4 and 20, which is 4. The length of each piece of fabric will be 4 meters.
A carpenter has two wooden planks, one 4 cm long and the other 20 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 4 and 20 2² = 4. The longest length of each piece is 4 cm.
To find the longest length of each piece of the two wooden planks, 4 cm and 20 cm, respectively.
We have to find the GCF of 4 and 20, which is 4 cm.
The longest length of each piece is 4 cm.
If the GCF of 4 and ‘b’ is 4, and the LCM is 20. Find ‘b’.
The value of ‘b’ is 20.
GCF x LCM = product of the numbers
4 × 20 = 4 × b
80 = 4b
b = 80 ÷ 4 = 20
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.
: She loves to read number jokes and games.