>>13495843>>135020782 laps is N miles
you first traveled N/2 miles at 60 mph
then if you traveled N/2 miles at 180 mph
the time spent in the first lap is N/2*1/(60mph) or N/120
the time spent on the second lap is N/2*1/180 or N/360
the total time if the average is 120mph is N/120
however, N/120 + N/360 = 4N/360 = N/90
and N/90 > N/120
therefore, you will need to have completed the second lap instantaneously (such that the time spent is 0) since the first lap took up the time which would have been needed to complete both laps, at 120mph
