Answer:
The minimum average speed needed in the second half is 270 km/hr
Step-by-step explanation
We can divide the track in two parts. For the first half of the track the average speed the car achieved was 230 km/hr and we need to make sure that the average speed of the full track is 250 km/hr. Then, we can calculate the average speed of the two parts of the track and force this to be equal to 250 km/hr. In equation, defining as the average speed of the second half:
Solving for
Therefore, achieving a speed of 270 km/hr in the second half would be enough to achieve an average speed of 250 on the track.