Question

You jog at 9.85 km/h for 8.10 km, then you jump into a car and drive an additional 16.2 km. With what average speed must you drive your car if your average speed for the entire 24.3 km is to be 21.0 km/h?

Answer 1

Average speed = Distance traveled / time taken

In jogging case Time taken = distance/speed

= 8.10/9.85 = 0.8223 hours

In care case Time taken = distance/speed

= 16.2/v hours

So total time taken , t = 0.8223+16.2/v

Total distance traveled = 8.10 km + 16.2 km = 24.30 km

So average speed
`= (24.30)/(0.8223+(16.2/v) ) =21 km/hr`

`v=48.38 km/hr`

Average speed you must drive your car if your average speed for the entire 24.3 km is to be 21.0 km/h = 48.38 km/hr