## Help JeffMath brain teasers require computations to solve.
Jeff likes racing his little sports car, but he knows that safety should always be kept in mind, so he practices regularly. On one particular day, Jeff goes out to the practice track and does two laps at an average of 100 km/h, two laps at an average of 102 km/h, two laps at an average of 140km/h and two laps at an average of 150 km/h. Now Jeff would like to know what his average speed was during that practice session. Can you help him?
## AnswerThe answer is 119 and NOT 123. How? Well, you have probably made the fatal assumption that time is not important here in Jeff's world and yet you should know that time is important everywhere.Hide ## What Next?
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