Product design question
Design a toothbrush.
- Product design
- Easy
Practice this question out loud. An AI interviewer asks it, follows up like a real interviewer would, and scores your answer. Type or speak.
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What this question tests
Foundational product design drill: can you start from a real user and job-to-be-done instead of jumping straight to features, even for a mundane object.
How to approach it
- Ask who: pick a specific user, e.g. a parent buying for a toddler, versus a general adult.
- Define the job to be done: effective plaque removal with minimal effort and minimal mess, twice a day.
- List pain points with existing toothbrushes: bristle wear signals, awkward angles for back teeth, kids not brushing long enough.
- Prioritize one pain point to solve deeply, e.g. under-brushing duration for kids, rather than redesigning everything.
- Propose a solution: a built-in timer with color change plus a bristle-wear indicator, keeping cost low.
- Define success: brushing duration compliance or repeat purchase rate if sold as a product line.
What a strong answer includes
- Picks a specific user segment (e.g. kids, or people with limited dexterity) rather than designing for 'everyone'.
- Identifies a real, non-obvious pain point like under-brushing duration or missed back-teeth coverage.
- Keeps the solution simple and manufacturable (timer + color cue) rather than over-engineering with unnecessary tech.
- Ties success to a behavior change metric, not just 'looks nice'.
Common mistakes
- Jumping straight to a fancy 'smart toothbrush with app' without justifying the added cost and complexity.
- Designing for a vague 'everyone' user instead of a specific segment with a specific pain point.
Likely follow-up questions
- Why did you choose that user segment over others?
- How would you keep manufacturing cost low while adding that feature?
More product design questions
- Design a TV for a car.Google · Product design · Hard
- Design a refrigerator for the blind.Google · Product design · Hard
- How do you design a camera for the elderly?Google · Product design · Medium
- Redesign Twitter for eCommerce.Shopify · Product design · Hard
- How would you go about designing a new location sharing app for Google?Google · Product design · Medium
- How would you improve Google Home?Google · Product design · Easy
More questions from Google
Learn the skill behind it
Chapters of the AI PM course that teach what this question tests.
- Chapter 4: Discovery and strategy for AI products
- Chapter 7: AI UX and human oversight: design for a system that is wrong sometimes
- Chapter 14: Get the job: the AI PM interview loop