Old Faithful Geyser in Yellowstone National Park erupts ever

Old Faithful Geyser in Yellowstone National Park erupts every 91 minutes. The time to wait for an eruption can be modeled with a uniform distribution. What is the probability that you will need to wait between 10 and 30 minutes for an eruption? (Give answer as a decimal.)

Solution

There is a certain eruption in every 91 minutes and the distribution of waiting time is uniform. So, the probability of uniform distribution = 1/91.

Hence, the probability of waiting time to be between 10 and 30 minutes = (30-10)*1/91 = 20/91 = 0.21978