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Park+·Product Manager·Onsite - Product Sense / Strategy·Intermediate

Intermediate
Jun 2026

Summary

Interviewed for a PM role at Park+ and got hit with a classic estimation question. Pretty short session from what I can tell, just one question but it required some real structured thinking on the spot.

Questions Asked (1)

Q1

How many trees are there in Delhi?

Product Analytics & MetricsAdaptability & Ambiguity
Author's notes

I panicked a little at first because I kept second-guessing my population density assumptions.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the scope: define what counts as a 'tree' (e.g., all trees in Delhi, including public and private lands) and the purpose (e.g., for urban planning or product strategy). Then, use a structured estimation approach, breaking down Delhi's area into zones (urban, suburban, rural) and estimating tree density per zone based on known data or reasonable assumptions. Finally, validate with sanity checks and discuss implications for Park+.

Pro tip: Acknowledge that this is a Fermi problem and that the process matters more than the exact number; show your ability to make reasonable assumptions and structure your thinking. Also, tie it back to Park+'s business—e.g., how understanding green cover could inform parking solutions or environmental initiatives.

1. Clarify the question

Ask clarifying questions to define 'tree' (e.g., include saplings? only trees above a certain height?) and the boundaries of Delhi (e.g., NCT of Delhi). Confirm the purpose to tailor the estimation.

2. Break down Delhi into zones

Divide Delhi into categories such as urban, suburban, and rural areas, or by land use (residential, commercial, parks, forests). Estimate the area of each zone.

3. Estimate tree density per zone

For each zone, estimate the number of trees per square kilometer based on typical densities (e.g., urban areas have fewer trees, parks have more). Use known data if available (e.g., Delhi's forest cover).

4. Calculate total trees

Multiply area by density for each zone and sum to get an estimate. Show your math clearly.

5. Sanity check and discuss implications

Compare your estimate with known figures (e.g., Delhi's tree census) and discuss potential errors. Relate the answer to Park+'s context, such as the importance of green spaces for urban mobility.

Key Points to Mention

  • Clarify assumptions: definition of a tree, boundaries of Delhi, and whether to include all trees or only those in public spaces.
  • Use a top-down approach: start with Delhi's total area (~1,484 km²) and break it down by land use.
  • Reference known data: Delhi's forest cover is about 20% of its area, but trees also exist outside forests.
  • Consider tree density: urban areas might have 100-200 trees per km², while parks and forests can have thousands.
  • Perform a sanity check: compare with Delhi's tree census (e.g., 2018 census counted ~4.2 million trees) to validate.
  • Tie back to Park+: Discuss how green cover affects parking demand, environmental sustainability, or product features like EV charging in green zones.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.