# How fast does he have to go the second 2 km to average 240 km/h for the entire course?

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A racecar driver drove, on a 4 km long racecourse, at an average speed of 120 km/h for the first 2 km. How fast does he have to go the second 2 km to average 240 km/h for the entire course?

posted May 8, 2014

+1 vote

AVG SPEED = Total Distance / Total Time

AVG Speed = 240 km/hr
Total Distance = 4 Km
Total Time = 2/120 + 2/X (assume X is the speed for next 2 KM)

So we have
240 = 4/(2/120 + 2/X)
or
60 = 1/(2/120 + 2/X)
or
1+120/X = 1

which is impossible...

+1 vote

he can't acheive average speed of 240 km/h for entire course.
because for avergae speed of 240 km/h for entire course he should complete his course in one minute but he already spent 1 minute for first two km.

–1 vote

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