You have to use the distance formula:
R x T = D (Rate x Time = Distance)
Fill in the information you know:
45 x T = 8.1 (divide both sides by 45 to get T by itself)
T = 8.1/45
T = .18 hours
(which is 60 x .18 = 10.8minutes)
58.285714286 minutes you drive 68 miles 60 minutes you drive 70 miles
8 minutes.
500 miles at 1000mph = 30 minutes.
15 minutes.
26.6666 minutes
22.8 minutes.
18 minutes.
25 minutes
It would take 12 minutes to drive 20 miles at 100 mph.
It would take about 46 minutes to drive 50 miles.
Four minutes at 60 mph
49 hours 55 minutes.