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How Many Piano Tuners Are in Chicago

How Many Piano Tuners Are in Chicago

The Question

Interview question: "How many piano tuners are in Chicago?"

This is the original Fermi estimation question, attributed to physicist Enrico Fermi who used it to test his students' ability to reason from first principles. You'll encounter it, or problems structurally identical to it, at Jane Street, Optiver, IMC, SIG, and Citadel Securities. It shows up in first-round screens and on-site interviews alike.

What...

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