Determine the factors of the numerator. Factors are numbers that, when multiplied together, equal that number. The factors of the numerator "3" are 1 and 3. There are no other whole numbers that equal 3 when they are multiplied together. Therefore, 1 and 3 are the only factors of the numerator 3.
Determine the factors of the denominator, "4." The factors of 4 are 1, 2 and 4 because 1 times 4 equals 4, and 2 times 2 equals 4. There are no other whole numbers that, when multiplied together, equal 4. Therefore, the factors of 4 are 1, 2 and 4.
Find the common factors between the numerator and the denominator. In other words, compare the factors to see which numbers are factors of both the numerator and the denominator. For 3/4, the only common factor is the number 1.
Choose the greatest common factor (GCF). For the fraction 3/4, the number 1 is the only common factor. Therefore, it is also the GCF.
Divide both the numerator and the denominator by their greatest common factor. When you divide 3 by 1 you still get 3. Divide 4 by 1 and you still get 4. Neither number can be reduced any further. Therefore, 3/4 is already in its lowest terms.
Follow the example in Section 1. Find all the factors of the numerator 10. The factors of 10 are 1, 2, 5 and 10, because 1 times 10 equals 10, and 2 times 5 equals 10. No other whole numbers, when multiplied by another whole number, equal 10. Therefore, there are no other factors of the number 10.
Find all the factors of the number 12. The factors of 12 are 1, 2, 3, 4, 6 and 12, because each of these numbers can be multiplied by another whole number to equal 12.
Study the factors of 10 and 12 and determine which factors are common to both numbers. The numbers 1 and 2 are the only common factors for 10 and 12. The other factors can be evenly divided into either 10 or 12, but not both.
Determine the greatest common factor (GCF) for the numbers 10 and 12. Since the common factors of 10 and 12 are 1 and 2 -- and 2 is greater than 1 -- the number 2 is the GCF.
Divide the numerator and the denominator by the greatest common factor, 2. Ten divided by 2 equals 5, and 12 divided by 2 equals 6. Therefore, simplifying the fraction 10/12, or reducing it to its lowest terms, it becomes 5/6.