Arithmetic/More About Multiplication/The Greatest Common Factor

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The Greatest common Factor (GCF) of two whole numbers is the highest number that can be divided by both of the original numbers to get a whole number result.

Finding the GCF of a number[edit]

  1. Write down to prime factorization of the two numbers.
  2. Find prime factors that are the same.
  3. Multiply the same prime factors together for the GCF.


  1. 28 = 2 \times 2 \times 7
    98 = 2 \times 7 \times 7
  2. Notice that two and seven are used in both the equations?
  3. 2 \times 7 = 14
    Therefore, the GCF of 28 and 98 is 14.