Final answer:
a) The probability of only one car arriving in the next hour is approximately 0.067.
b) The probability of more than 20 cars arriving in the next 3 hours can be found by subtracting the probability of 20 or fewer cars from 1.
Step-by-step explanation:
a) To determine the probability that only one car will arrive in the next hour, we need to use the Poisson distribution formula. The Poisson distribution formula is P(x; μ) = (e^(-μ) * μ^x) / x!, where x is the number of events and μ is the mean. In this case, x = 1 and μ = 5 (since the mean is given as 5 cars per hour). Plugging these values into the formula, we get P(1; 5) = (e^(-5) * 5^1) / 1! ≈ 0.067.
b) To compute the probability that more than 20 cars will arrive in the next 3 hours, we can use the complement rule. First, we find the probability that 20 or fewer cars will arrive in the next 3 hours. Using the Poisson distribution formula with x = 20 and μ = 5 (since the mean is given as 5 cars per hour), we get P(≤20; 15) = ∑(i=0 to 20) (e^(-15) * 15^i) / i!. Then, we subtract this probability from 1 to find the probability of more than 20 cars arriving.