MediumBrain Teasers

Two Eggs, 100 Floors

GoogleGoldman Sachs

You have 2 identical eggs and a 100-floor building. An egg breaks if dropped from floor F or above. Minimise the number of drops in the worst case needed to find F with certainty. How many drops?

Approach

First drop high, then shorten the gaps each time.

Solve n(n+1)/2 ≥ 100.