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Estimationstandard
How many elevators are there in Manhattan?
How to approach it
Segment buildings by height, because a five-story walk-up and a sixty-story office tower have very different elevator counts.
How a strong answer opens
“I'll segment buildings by height and type, because a five-story walk-up and a sixty-story tower have very different elevator counts.”
Outline of a strong answer
Try answering out loud for a few minutes before you open this.
- Clarify: passenger and freight, all of Manhattan
- Estimate buildings by type and height
- Elevators per building type
- Multiply buildings by elevators per building and sum across types
- Sanity-check using people per elevator
Where this question usually goes wrong
Applying one elevator count to every building, which misses that a few tall towers hold a large share of the elevators.
Learn the method
Top-down and bottom-up in Module 3, Estimation.
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