A mean car...

Calculus Level 2

It took me one minute to complete a one kilometer first lap on a racetrack. How long does my second lap should last if I want to achieve a 120 km/h average speed for the two laps combined?

20 s 60 s 30 s None of these

Tim Raccoon by Tim Raccoon , 33, France

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1 solution

Tim Raccoon
Aug 21, 2018

Correct answer is " None of these " as this impossible problem would require a teleportation to the finish line.

Explication : we would like to achieve an average speed of 120 km/h for 2 laps of 1 km each so 2 km in total. At 120 km/h, it only takes a minute to complete the 2 laps but we already spent 1 minute during the first kilometer lap so the best we could do would be to approach a 120 km/h average speed but never reaching it.

  • Example 1 : Even if we speed up to 180 km/h during the second lap, it takes us 20 s to finish it. So we spent 60 + 20 = 80 s to finish the 2 km race so an average speed of 90 km/h.
  • Example 2 : Even if we speed up to 3600 km/h during the second lap, it takes us 1 s to finish it. So we spent 60 + 1 = 61 s to finish the 2 km race so an average speed of 118 km/h.
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