As we have seen there is an own word for
1/2 (un medio)
1/3 (un tercio)
Then from four to ten the fractions are identical with the ordinal numbers.
Beyond ten the cardinal number is appended with -avo, -ava, avas, avos.

Furthermore it is to be noted that the single number is appended directly to the figures of tens (treinta y uno but treintaiunavo).

Moreover, please note that in Latin and Southern America the fractions are used as ordinals.