Reduce the fraction to be halved to its lowest terms. To reduce or simplify the fraction, you need to eliminate the numerator and denominator's greatest common factor, or the largest value that both share as factors. For an example, using the fraction 8/10, the factors of the numerator 8 are 1, 2, 4 and 8, and the factors of the denominator 10 are 1, 2, 5 and 10. For the numbers 8 and 10, the greatest common factor is 2. Eight divided by (8/2) equals 4 and 10/2 equals 5, so 8/10 reduced equals 4/5.
Divide the reduced fraction's numerator by 2 if it is even. To halve 4/5, divide the numerator 4 by 2 and the final fraction is 2/5.
Multiply the reduce fraction's denominator by 2 if the numerator is odd. As an example, the fraction 1/3 has an odd numerator. Multiply the denominator of 3 by 2 and the final fraction is 1/6.