Estimation question

How many elevators are there in a building?

Practice this question out loud. An AI interviewer asks it, follows up like a real interviewer would, and scores your answer. Type or speak.

What this question tests

Estimation: can you reason through a physical-world Fermi problem by anchoring on building height and code/usage norms.

Clarify scope: estimate elevators in one representative large building (e.g. a 40-floor office tower) versus a whole city.
State an assumption for building height, e.g. 40 floors, and typical elevator-to-floor ratios in commercial code (roughly 1 elevator per 8-10 floors of capacity need).
Adjust for building type: office towers need more elevators for peak-hour capacity than residential buildings of the same height.
Estimate a range, e.g. 6-10 elevators for a 40-floor office tower, based on the ratio.
If scoped to a city, multiply by an estimated count of buildings above a certain height threshold in that city.
State what data would refine it: actual elevator codes (like ASME A17.1 guidance) or a sample of known buildings.

Explicitly picks a scope (one building vs a city) since the question is ambiguous, and states the choice.
Uses a floor-to-elevator ratio grounded in real-world code/capacity logic, not a random guess.
Distinguishes building types (office vs residential) since elevator density differs meaningfully.
Gives a clear final range with assumptions labeled, not a single falsely-precise number.

Not clarifying scope and guessing a number for an undefined building.
Ignoring that elevator count scales with peak-hour capacity needs, not just height.

How would your estimate change for a residential building versus an office tower?
What real-world data source would you use to sanity check this?