Estimation question
How many bricks are there in New York?
- Estimation
- Easy
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What this question tests
Classic estimation skill through structured decomposition, not the exact number, checking assumptions are stated clearly.
How to approach it
- Restate the question: total number of bricks across all structures in New York City.
- Estimate the number of brick buildings in the city, stating a rough share of total buildings assumed to be brick construction.
- Estimate an average building's brick facade area, distinguishing rough categories like small residential versus larger structures if useful.
- Estimate bricks per square foot of facade based on typical brick and mortar dimensions, stated as an assumption.
- Multiply building count by average facade area by bricks per square foot to reach a total, showing the arithmetic clearly.
- State a final illustrative range and flag building count and facade coverage as the biggest sources of uncertainty.
What a strong answer includes
- Breaks the estimate into building count, facade area, and bricks per square foot explicitly, rather than guessing one giant number.
- States a clear bricks-per-square-foot assumption grounded in typical physical brick dimensions, showing genuine reasoning rather than a random guess.
- Shows the full multiplication chain clearly so the logic can be audited step by step.
- Flags which assumption drives the most uncertainty, likely the share of buildings that are brick construction, showing awareness of estimate sensitivity.
Common mistakes
- Guessing a single large number with no structured decomposition.
- Not stating a physical basis for bricks per square foot, making the estimate ungrounded.
- Skipping a sanity check or range, presenting one number as if precise.
Likely follow-up questions
- How would your estimate change if you only counted residential buildings versus all buildings?
- What's the biggest source of uncertainty in your estimate?
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Learn the skill behind it
Chapters of the AI PM course that teach what this question tests.
- Chapter 2: Data fluency: SQL, logs, and reading the truth yourself
- Chapter 9: Prove it paid off: outcomes, economics, and pricing
- Chapter 14: Get the job: the AI PM interview loop