Problem of the Week 921

The Egg Drop

Suppose that we wish to know which window in a 36-story building are safe to drop eggs from, and which will cause the eggs to break on landing. We make a few assumptions:

If only one egg is available and we wish to be sure of obtaining the right result, the experiment can be carried out in only one way. Drop the egg from the first-floor window; if it survives, drop it from the second floor window. Continue upward until it breaks. In the worst case, this method may require 36 droppings. Suppose 2 eggs area available. What is the least number of egg-droppings that is guaranteed to work in all cases?

Source: St. Olaf College Problem of the Week, Oct. 17, 2000

(It turns out that this is a former problem of the week and has appeared in Which Way Did the Bicycle Go? (Konhauser/Velleman/Wagon). My apologies, but it is a good problem.)

© Copyright 2000 Stan Wagon. Reproduced with permission.

01 November 2000