Estimation question

How many elevators are needed in a mall?

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 using traffic and capacity reasoning: can you build a defensible number from foot traffic, floor count, and elevator throughput.

Estimate mall size, assume a large mall with 4 floors and roughly 20,000 visitors on a peak day.
Estimate peak hour traffic, assume 15 percent of daily visitors arrive in the busiest hour, roughly 3,000 people.
Estimate how many of those need an elevator versus escalators or stairs, assume 20 percent, mostly those with strollers, mobility needs, or carrying heavy shopping, roughly 600 people per peak hour.
Estimate elevator throughput, assume each elevator holds 10 people and completes a round trip in 2 minutes, giving 5 trips per hour, roughly 50 people moved per hour per elevator.
Divide demand by capacity: 600 divided by 50 gives roughly 12 elevators needed at peak, then round down slightly accounting for escalators absorbing some overflow, landing around 8 to 10 elevators.
State the final estimate as a range and name peak hour demand as the most sensitive assumption.

Builds from foot traffic to elevator specific demand to capacity per elevator, a full and logical chain.
Adjusts for escalators absorbing some demand, showing awareness that elevators are not the only vertical transport.
States the final number as a range tied to explicit assumptions rather than a single guessed figure.

Estimating total mall visitors and assuming they all need an elevator, ignoring escalators and stairs.
Skipping the elevator capacity and round trip time calculation and jumping to a guessed count.

Chapters of the AI PM course that teach what this question tests.