Find the LCM of the fractions 5/6, 10/9 and 20/27.

LCM of fractions = LCM of the numerators / HCF of the denominators. LCM(5, 10, 20) = 20 and HCF(6, 9, 27) = 3, so the answer is 20/3. Swapping the two rules gives 5/54, which is the HCF of the three fractions; 20/27 just picks the largest fraction given; 10/3 comes from using 6 instead of 3 as the HCF of the denominators.