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?

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

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

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