You jog at 6.8 mi/h for 5.0 mi, then you jump into a car and drive for another 5.0 mi. With what average speed must you drive if your average speed for the enti

Question

You jog at 6.8 mi/h for 5.0 mi, then you jump into a car and drive for another 5.0 mi. With what average speed must you drive if your average speed for the entire 10.0 miles is to be 10.0 mi/h?

 

mi/h

Answer 1

traveling 10 miles with an average speed of 10 mi/h means it took 1 hour total time

 

for the jogging portion of the trip, time = distance/speed = 5 mi / 6.8 mi/h = .7353 hours

 

therefore the driving portion took .2647 hours.

 

Therefore average speed driving = distance / time = 5 mi / .2647 h = 18.9 mi/h

 

In other words, jogging time + driving time = total time

 

5/6.8 + 5/x = 10/10

 

.7353 + 5/x = 1

 

5/x = .2647

 

x = 5/.2647

 

x = 18.9 mi/h    same answer