Formação de frações - Resposta

Como pode formar frações a partir das seguintes posições ou rankings:

3rd
1/3rd;  2/3rd;

4th
1/4th;  2/4th;  3/4th

5th;
1/5th;  2/5th;  3/5th;  4/5th;

7th;
1/7th;  2/7th;  3/7th;  4/7th;  5/7th;  6/7th

20th;
1/20th;  2/20th;  3/20th;  4/20th;  5/20th;  6/20th;  7/20th; --------; 19/20th

22nd;
1/22nd; ----------------------------------------; 21/22nd

39th;
1/39th; -------------------------------------; 38/39th

41st;
1/41st; --------------------------------------; 40/41st
11th;

16th
1/16th; ----------------------------------; 15/16th

13th
1/13th; ---------------------------------; 12/13th.