1. The problem statement, all variables and given/known data A racecar driver must average 200 km/h over the course of a time trial lasting ten laps. If the first nine laps were done at 199 km/h, what average speed should be maintained for the last lap? 2. Relevant equations avg =distance/time 3. The attempt at a solution He drove at 199 for 9 laps. 199*9=1791 He needed to average 200 for 10 laps. 2000 2000-1791=209. The answer is 209.5 km/h, but why?? I also tried dividing 199 by 9 and 200 by 10, averaging to get 21.05, and then multiplying by 10, but that isn't working either. I'm having a hard time finding an appropriate equation, so I was trying to think it through logically. It didn't work. Thanks in advance for an answer!