Abby’s bus left at 2:00, going southbound at 55 mph. Bob’s went northbound starting at 3:00, going only 45 mph. How long will it take for them to get 420 miles apart?
Round to the nearest tenth if necessary
at time t hours after 2:00, the distance d between the buses is
d = 55t + 45(t-1)
so, the number of hours (t) is
55t + 45(t-1) = 420
t = 4 13/20 hrs = 4 hr 39 min