Auto Arrival
1. The problem states that autos arrive at a tollbooth at a rate of 50 autos per minute from 12:00 to 13:00.
2. We want to find the probability that the next auto will arrive within 3 seconds.
3. Since arrivals are at a rate of 50 autos/minute, convert this rate to autos per second:
$$\lambda = \frac{50}{60} = \frac{5}{6} \text{ autos per second}$$
4. Assuming arrivals follow a Poisson process, the time between arrivals is modeled as an exponential random variable with parameter $\lambda = \frac{5}{6}$.
5. The probability that the next auto arrives within 3 seconds is the cumulative distribution function (CDF) of the exponential distribution:
$$P(T \leq 3) = 1 - e^{-\lambda \times 3} = 1 - e^{-\frac{5}{6} \times 3} = 1 - e^{-2.5}$$
6. Calculate the numerical value:
$$1 - e^{-2.5} \approx 1 - 0.0821 = 0.9179$$
7. Therefore, the probability that the next auto arrives within 3 seconds is approximately 0.918.