Q: Light bulbs last on average 1000 hours (exponential). Find P(last > 2000 hours). λ = 1/1000. P(X > 2000) = e^(-λx) = e^(-2000/1000) = e^(-2) = 0.1353. About 13.5% survive past 2000 hours - memoryless: a used 1000-hour bulb is as good as new!