The tropical storm-force winds of a category 3 hurricane are forecast to intersect the decision arc for your community in 36 hours. for a hurricane of category 4 intensity, it is estimated that your community will need 20 hours to evacuate to safety. how much time is there before the evacuation should be started?

With the category 3 hurricane and category 4 hurricane, the community will have the time given before the evacuation should be started by subtracting the the number of hours needed to evacuate from the time from the decision arc. From the given,

h = 36 hours - 20 hours

h = 16 hours

Thus, the community is given 16 hours.