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 12 and 42.
The greatest common factor of 12 and 42 is 6. 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 12 and 42, a few methods are described below -
Steps to find the GCF of 12 and 42 using the listing of factors
Step 1: Firstly, list the factors of each number
Factors of 12 = 1, 2, 3, 4, 6, 12.
Factors of 42 = 1, 2, 3, 6, 7, 14, 21, 42.
Step 2: Now, identify the common factors of them Common factors of 12 and 42: 1, 2, 3, 6.
Step 3: Choose the largest factor
The largest factor that both numbers have is 6.
The GCF of 12 and 42 is 6.
To find the GCF of 12 and 42 using the Prime Factorization Method, follow these steps:
Step 1: Find the prime factors of each number
Prime Factors of 12: 12 = 2 x 2 x 3 = 2² x 3
Prime Factors of 42: 42 = 2 x 3 x 7
Step 2: Now, identify the common prime factors
The common prime factors are: 2 x 3
Step 3: Multiply the common prime factors 2 x 3 = 6.
The Greatest Common Factor of 12 and 42 is 6.
Find the GCF of 12 and 42 using the division method or Euclidean Algorithm Method. Follow these steps:
Step 1: First, divide the larger number by the smaller number
Here, divide 42 by 12 42 ÷ 12 = 3 (quotient),
The remainder is calculated as 42 − (12×3) = 6
The remainder is 6, not zero, so continue the process
Step 2: Now divide the previous divisor (12) by the previous remainder (6)
Divide 12 by 6 12 ÷ 6 = 2 (quotient), remainder = 12 − (6×2) = 0
The remainder is zero, the divisor will become the GCF.
The GCF of 12 and 42 is 6.
Finding the GCF of 12 and 42 looks simple, but students often make mistakes while calculating the GCF. Here are some common mistakes to be avoided by the students.
A teacher has 12 notebooks and 42 markers. 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 12 and 42 GCF of 12 and 42 2 x 3 = 6.
There are 6 equal groups 12 ÷ 6 = 2 42 ÷ 6 = 7
There will be 6 groups, and each group gets 2 notebooks and 7 markers.
As the GCF of 12 and 42 is 6, the teacher can make 6 groups. Now divide 12 and 42 by 6. Each group gets 2 notebooks and 7 markers.
A school has 12 red flags and 42 blue flags. They want to arrange them in rows with the same number of flags in each row, using the largest possible number of flags per row. How many flags will be in each row?
GCF of 12 and 42 2 x 3 = 6.
So each row will have 6 flags.
There are 12 red and 42 blue flags.
To find the total number of flags in each row, we should find the GCF of 12 and 42.
There will be 6 flags in each row.
A tailor has 12 meters of red fabric and 42 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 12 and 42
The GCF of 12 and 42 2 x 3 = 6.
The fabric is 6 meters long.
For calculating the longest length of the fabric first, we need to calculate the GCF of 12 and 42, which is 6. The length of each piece of the fabric will be 6 meters.
A carpenter has two wooden planks, one 12 cm long and the other 42 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 12 and 42 2 x 3 = 6.
The longest length of each piece is 6 cm.
To find the longest length of each piece of the two wooden planks, 12 cm and 42 cm, respectively. We have to find the GCF of 12 and 42, which is 6 cm. The longest length of each piece is 6 cm.
If the GCF of 12 and ‘a’ is 6, and the LCM is 84. Find ‘a’.
The value of ‘a’ is 42.
GCF x LCM = product of the numbers 6 × 84 = 12 × a
504 = 12a
a = 504 ÷ 12 = 42
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.