Students learn that a fraction is in lowest terms if the Greatest Common Factor of the numerator and denominator is 1. For example, 3/5 is in lowest terms, because the Greatest Common Factor of 3 and 5 is 1. However, 3/6 is not in lowest terms, because the Greatest Common Factor of 3 and 6 is 3. Students also learn that a fraction can be rewritten in lowest terms by dividing the numerator and denominator by their Greatest Common Factor. For example, to write 10/15 in lowest terms, divide the numerator and denominator by their Greatest Common Factor of 5, to get 2/3.

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