The $200K Guesstimate: Fermi Math for Tech, Consulting, Startup & Finance Interviews

Big interview questions are rarely about finding one perfect number. They are about how you think when the data is incomplete. The $200K Guesstimate teaches a practical framework for tackling Fermi and estimation questions across tech, consulting, startup, and finance interviews. Instead of memorizing famous answers, you learn a repeatable process: DECOMPOSE → ANCHOR → SANITY-CHECK Across 100 fully worked problems, you will practice how to break unfamiliar questions into manageable parts, choose defensible assumptions, keep units and orders of magnitude under control, stress-test uncertain inputs, and communicate your reasoning clearly under pressure. Inside you will find: - 100 worked estimation and interview problems - Tech, consulting, startup/VC, quant, finance, and classic Fermi examples - Step-by-step decomposition and sanity-check methods - Mental-math and calibration techniques - Sensitivity analysis and uncertainty handling - Sample spoken answers and common traps - A self-scoring rubric - 2-week and 30-day practice plans >This is an interview-preparation book about structured reasoning-not a collection of numbers to memorize. The goal is to make your thinking visible, adaptable, and defensible when the answer is uncertain.