if the average speed of ALL 5 coasters is no more than 91 mph then that last coaster has to be 100 mph to reach a speed of 91 on average. if superman goes at 99 then the average would be only 90.8 if it's at 100, the average would be 91 exactly
83+85+92+95+s=5(91)
s = 455-355
s = 100
I agree