Shouldn't your question be "How many minutes does it take to travel one mile"?
There are 60 minutes in an hour so 45 mph =
45 / 60 = .75 miles per minute
If we take the reciprocal we will get minutes per mile:
1 / .75 miles per minute = 1.3333333333 minutes per mile, so it will take 1.33333333 minutes.
