Math
Queues: why 90 % busy means waiting
Run an event-based FIFO M/M/1 queue. Inspect congestion, measured residence times, stable and overloaded regimes, and the finite-run approach to Little’s law.

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Arrivals and service times are sampled exponentially. Compare time-averaged occupancy with throughput × residence time. When λ ≥ μ there is no finite stationary mean.
Equations used in the module
Equations ρ = λ/μ M/M/1, ρ < 1: L = ρ/(1−ρ); W = 1/(μ−λ) Little: L = λeffective W For finite runs, customers still present contribute a boundary term


