Solve a set of interview puzzles: estimate the probability of seeing at least one car in a half hour when the one-hour probability is 0.99; compute how long two crews taking 6 and 8 days individually need together; and design a minimum-test strategy to find two working batteries when 4 of 8 batteries work and a toy starts only with two working batteries. ### Constraints & Assumptions - Assume independent Poisson-like arrivals for the car problem. - For the work-rate problem, rates add linearly. - For the battery problem, each test checks a pair and succeeds only if both are working. - The goal is finding any two working batteries, not classifying all batteries. ### Clarifying Questions to Ask - Can I assume arrivals in disjoint half-hour intervals are independent? - Do failed battery tests reveal whether zero or one battery worked? - Do we need a worst-case guarantee or expected number of tests? - Can batteries be labeled and tested in any chosen pairs? ### What a Strong Answer Covers ```premium-lock What a Strong Answer Covers ``` ### Follow-up Questions - How would the battery answer change if 3 of 8 worked? - What if car arrivals are not independent? - How would you explain the work-rate calculation without fractions? - How do you avoid over-talking while solving puzzles live?