Question
Sat September 29, 2012 By:
 

A jogger desires to run a certain course in 1/4 less time than she usually takes. By what percent must she increase her average running speed to accomplish this goal?

Expert Reply
Sat September 29, 2012

Let the jogger usually takes t minutes to cover a distance of x m.

So, his usual speed is x/t m/s.

 

Since, he desires to take 1/4 less time than he takes usually so, he desires to take 3t/4 minutes to cover x m.

In this case his speed has to be x/(3t/4) = 4x/3t m/s.

 

The speed that has to increase to desired the Jogger's goal = (4x/3t - x/t) m/s = x/3t m/s.

So, the percentage of speed the Jogger needs to increase = increase speed/original speed × 100 = 1/3 × 100 = 33.33 % (approx)

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