Is the word quinto the same in Brazilian and European Portuguese?

Yes

The word "quinto" is identical in meaning, spelling, and grammar in both Brazilian and Continental Portuguese. The only difference lies in pronunciation. In Brazilian Portuguese, the "n" is typically treated as a nasalization of the preceding vowel (making the "i" nasalized, as in [kĩtu]), and the "t" is a standard alveolar [t]. In Continental Portuguese, the "n" is often more clearly articulated as a consonant, and the "t" is dental [t̪], with the vowels being more closed or reduced.

Brazilian Portuguese

1. Ele é o quinto da fila. (He is the fifth in line.)
2. Eu comi um quinto da pizza. (I ate a fifth of the pizza.)
3. Este é o meu quinto carro. (This is my fifth car.)
4. O quinto andar é o mais caro. (The fifth floor is the most expensive.)
5. Ele chegou em quinto lugar na corrida. (He finished in fifth place in the race.)

Continental Portuguese

1. Ele é o quinto da fila. (He is the fifth in line.)
2. Comi uma quinta parte da pizza. (I ate a fifth of the pizza.)
3. Este é o meu quinto automóvel. (This is my fifth car.)
4. O quinto andar é o mais caro. (The fifth floor is the most expensive.)
5. Ele ficou em quinto lugar na corrida. (He finished in fifth place in the race.)