sorry gave wrong address beforea motorist drives 450 miles i

sorry gave wrong address before...a motorist drives 450 miles in 8 hours. on the journey he averages 60 mph before noon and 50 mph after. what were his departure and arrival times? i used formula d=rt, d=450. i know i don\'t add the 2 rates, but do i average the averages to solve for t (r=55) , 8.01 ...wrong! i also found the average travel time for the whole trip is 56.25 mph ...doesn\'t help. how do i solve for t?
450=60 t + 50 t???
thanx for reading

Solution

t = time driving 60
450 = 60t + 50*(8-t)
450 = 60t + 400-50t
50 = 10t
t = 5 hours
1200 - 500 = 0700 departure