To write "55th" in words, you would write it as "fifty-fifth." This follows the standard English convention for ordinal numbers, where numbers are written out as words when indicating their position in a sequence.
Fifth of May, Two Thousand and Eleven. V V XI
one and one-fifth
Fifth Century - 5th Century.
10 to the fifth power = 105
first second third fourth fifth ... As a rule you add the suffix 'th' to a cardinal to get an ordinal,but 1,2, and 3 are special and there are some spelling changes: fifth and twelfth , fiftieth,etc.
The fourth prime is 7 and the fifth is 11.
One-fifth is 1/5 or 0.2
0.2
After the fourth.
0.2
five and one fifth = 5 1/5