Deriving the Number of Hexagon Panels on a Classic Soccer Ball

Quick Overview

An analytical-thinking question from a PM interview that asks how many hexagon panels a classic soccer ball has and how you would work it out. It tests clarifying an ambiguous object, choosing between a structural argument and a surface-area estimate, getting the arithmetic right and sanity-checking the result.

Deriving the Number of Hexagon Panels on a Classic Soccer Ball

Company: Amazon

Role: Product Manager

Category: Product / Decision Making

Difficulty: medium

Interview Round: Other

How many hexagons does a football have? Commit to a number and walk the interviewer through the reasoning that gets you there; the way you reach the answer matters as much as the answer. ```hint Look at one corner Instead of measuring panels, consider how they fit together: which shapes meet at each corner of the ball, and how many panels share each seam. Facts like these can be turned into equations. ``` ### Clarifying Questions - Which ball is meant: the classic soccer ball with black pentagons and white hexagons, an American football, or a modern match ball whose panels have other shapes? - Can I look at a ball or a picture of one, or should I reason it out from memory? - Is an exact count expected, or is a well-reasoned estimate with a sanity check enough? ### What a Strong Answer Covers - Settling which ball is meant and stating the assumptions about its panels before counting anything. - A structured method: either a geometric argument that yields an exact count or a surface-area estimate with every input labeled as an assumption. - Correct arithmetic and a check that the final numbers are consistent with each other and with the ball's pattern. - Judgment about which method is more reliable and how sensitive an estimate is to its inputs. ### Follow-up Questions - How many pentagons does the same ball have, and how many seams must be stitched to assemble it? - If you knew only the ball's diameter and a rough panel width, how would you estimate the count, and how far off could you be? - A manufacturer wants a ball made of fewer, larger panels. What changes for players, and what trade-offs come with it?

Overview: An analytical-thinking question from a PM interview that asks how many hexagon panels a classic soccer ball has and how you would work it out. It tests clarifying an ambiguous object, choosing between a structural argument and a surface-area estimate, getting the arithmetic right and sanity-checking the result.

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Amazon
May 31, 2024
mediumProduct ManagerOtherProduct / Decision Making
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How many hexagons does a football have? Commit to a number and walk the interviewer through the reasoning that gets you there; the way you reach the answer matters as much as the answer.

Clarifying Questions Guidance

  • Which ball is meant: the classic soccer ball with black pentagons and white hexagons, an American football, or a modern match ball whose panels have other shapes?
  • Can I look at a ball or a picture of one, or should I reason it out from memory?
  • Is an exact count expected, or is a well-reasoned estimate with a sanity check enough?

What a Strong Answer Covers Guidance

  • Settling which ball is meant and stating the assumptions about its panels before counting anything.
  • A structured method: either a geometric argument that yields an exact count or a surface-area estimate with every input labeled as an assumption.
  • Correct arithmetic and a check that the final numbers are consistent with each other and with the ball's pattern.
  • Judgment about which method is more reliable and how sensitive an estimate is to its inputs.

Follow-up Questions Guidance

  • How many pentagons does the same ball have, and how many seams must be stitched to assemble it?
  • If you knew only the ball's diameter and a rough panel width, how would you estimate the count, and how far off could you be?
  • A manufacturer wants a ball made of fewer, larger panels. What changes for players, and what trade-offs come with it?