It takes approximately 1.54 hours, or 1 hour 32 minutes and 18.46 seconds, to travel 100 miles at a rate of 65 mph. The formula for determining time is based on the formula rate multiplied by time equals distance. The unknown element, time, is determined by dividing distance by rate.
In this case, dividing 100 miles by 65 mph yields the time necessary for travel. The rate of 65 miles per hour must be constant in order for this time to be true. Using the basic formula of rate multiplied by time equals distance, one can determine any one of the three elements if the other two are known quantities. Determining rate requires dividing distance by time.