one hour
1hr 20mins
36 minutes.
2 hours
100/80 = 1.25 hours
About 2 hours and 20 minutes
2 hours
2.977 hours
1 hour 32 minutes.
2 and a half hours
1hour 10minutes 35.3seconds (rounded)
About 2 hours 30 minutes.
Divide 317 miles by 100 miles per hour to obtain: 317 miles / (100 miles per hour) = 317 miles * 1 hour / 100 miles ≈ 3.17 hours