posted by Anonymous .
A bus started out going 20 miles per hour on the highway. One hour later it drove 40 miles per hour on the freeway. How long did it take to go 140 miles?
acceleartion= (40-20)/60 min
d= vi*t+1/2 at
140=20*t+1/2(20/60)t^2 solve for t, in minutes.