This is a wonderful puzzle shared by a good friend Alok Aggarwal, who lives in California and are a family of math wizards (which includes him as well!).
This puzzle is a variation of puzzle #94 (https://alokgoyal1971.com/2015/03/01/puzzle-94-two-eggs-and-a-building/), where with two eggs and a building with 100 floors, one had to figure out an optimal strategy for finding the lowest floor at which an egg will break when dropped. Optimality is defined by least number of trials.
For the same problem, assume you have 81 floors and 4 eggs, what is the optimal strategy?
Happy egging again!