Verified Answer :

There is an infinite number of equivalents to 1/81, for example:

2/162 because 1 2 = 2 and 81 2 = 162
3/243 because 1 3 = 3 and 81 3 = 243
4/328 because 1 4 = 4 and 81 4 = 328

1.81 is the most logical answer