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Google·Product Manager·Onsite - Product Sense / Strategy·Intermediate

Intermediate
May 2026

Summary

PM interview at Google with a classic estimation question. Pretty short and to the point, nothing wild to report.

Questions Asked (1)

Q1

How many grains of rice are in a 10kg bag?

Product Analytics & MetricsAdaptability & Ambiguity
Author's notes

Classic fermi estimation.

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AI HintsAI Generated

Suggested Approach

Break the problem into measurable components: estimate the weight of a single grain of rice, then divide 10kg by that weight. State your assumptions clearly and show the calculation, while acknowledging the inherent uncertainty in the estimate.

Pro tip: After arriving at a number, briefly discuss how you would validate it (e.g., weighing a small sample) and how the estimate could inform product decisions, showing you think beyond the math.

1. Clarify the question and scope

Ask clarifying questions to ensure you understand what is being asked, such as whether the bag contains long-grain or short-grain rice, and whether it's a standard 10kg bag with no other contents.

2. Estimate the weight of one grain

Use known references: a typical grain of rice weighs about 0.02 to 0.03 grams. You can also estimate by recalling that a cup of rice (about 200g) contains roughly 7,000-8,000 grains.

3. Calculate the number of grains

Divide 10,000 grams by the estimated weight per grain. For example, at 0.025g per grain, 10,000 / 0.025 = 400,000 grains.

4. Sanity-check and refine

Consider if the result seems reasonable: a 10kg bag is large, so hundreds of thousands of grains makes sense. If needed, adjust for variables like grain size or moisture content.

5. Communicate assumptions and confidence

Clearly state your assumptions (e.g., average grain weight) and acknowledge that the answer is an estimate with a range (e.g., 300,000 to 500,000 grains).

Key Points to Mention

  • The importance of stating assumptions explicitly (e.g., average grain weight).
  • Using a reference point: a cup of rice weighs about 200g and contains ~7,000 grains.
  • The calculation: 10,000g / 0.025g per grain = 400,000 grains.
  • Acknowledging variability: grain size, type, and moisture can affect the estimate.
  • Providing a range rather than a single number to reflect uncertainty.
  • Relating the estimation process to product metrics or decision-making (e.g., inventory management).

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