Brain Teasers & Mental Math
Estimate how many barbers/hair salons are needed to serve the US population.
Model answer
Bottom-up via demand. ~330M people; assume average ~8 haircuts/person/year (men more frequent, kids and some women less/DIY) → ~330M × 8 ≈ ~2.6B haircuts/year. One chair does ~10 cuts/day × ~300 days…
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