"The sixtieth woman is tall."
Translation:A șaizecea femeie este înaltă.
Try to think of it by grouping it like "<<The sixtieth>> woman". As in: "- Which woman? - The sixtieth."
So "the sixtieth" would become "a șaizecea", which is articulated.
So now you can ask yourself: "- The sixtieth WHAT? - The sixtieth WOMAN." (as in "The sixtieth <something>.")
Makes any sense?
Indeed. Moreover, think to ordinal numerals like something which is always articulate (same as in English). If the noun follows, then it is not articulated. But when the noun precedes (for emphasis, whatever, or in some special cases), then the noun is articulated too. For example, ”fata a cincea” or ”omul al doilea”, but ”a cincea fată” and ”al doilea om”. The reverse formulations (”fată a cincea”, ”om al doilea”, ”a cincea fata”, ”al doilea omul”) are all wrong and sound quite odd and funny for Romanian ears.