i think the total distance travelled is 200 miles... he travelled at 40mph for 1hr and 40 mins. and at 50 mph for the remaining time.

therefore distance travelled is

40*100(mins)/60+ 50*80/60+ 50*80/60 =400/6 + 400/6 + 400/6

= 1200/6

=200 miles..

400/6 is also the 1/3rd of the distance travelled... is it correct... correct me if i am wrong....