Speed is calculated using the formula distance divided by time. For a distance of 26.2 miles, and a time of 3 hours and 40 minutes, we first convert the time to make it solely in terms of hours. 40 minutes is 2/3 of an hour, so this is a total time of 3 2/3 or 11/3 hours. If we divide 26.2 miles by 11/3 hours, we get a resulting speed of 7.14 miles/hour.