A person travels by car from one city to another with different constant speeds between a pair of cities. She drives for 30.3 min at 85.2 km/h, 14.4 min at 91.1 km/h, and 48.9 min at 43.1 km/h, and spends 19.1 min eating lunch and buying gas. The distance between the initial and final cities along this route is 100.0165 km. Find the average speed for the trip. Answer in units of km/h.
The Attempt at a Solution
I added up all of the times (30.3 min+14.4 min+48.9 min) and got 93.6 min. I converted this to hours by dividing by 60 and got 1.56 hours. Then I divided 100.0165 by 1.56 hours and got 64.11314103. (I use the whole solution. I don't round unless I have to.) It was incorrect. If average speed equals total distance over total time, then what did I do wrong? I know I don't use that 19.2 min because it's just extra time that was spent eating and buying gas. I don't need that. So what am I doing wrong?