Final answer:
The car was likely traveling 70 km/h between the periods it was recorded at 30 km/h and 100 km/h. Without precise acceleration details, the exact time or track location for this speed cannot be determined. However, it is within a reasonable inference that this speed occurred during the three hours of speed increase.
Step-by-step explanation:
The question posed is about determining when a car was traveling at a speed of 70 km/h given the context of various speeds and conditions. In the scenarios provided, the car's speeds range significantly, but the specific instance of the car traveling 70 km/h is not directly mentioned. Therefore, we have to deduce based on the changes in speed over time. At some point between when the car was traveling at 30 km/h four hours ago and reaching 100 km/h one hour ago, it must have passed through the speed of 70 km/h unless there was an instantaneous jump in speed, which is physically improbable.
Considering that the car consistently increased its speed, it is reasonable to believe that at some interval during this three-hour window, the car was traveling at 70 km/h. Since no further details about the acceleration rate are provided, we cannot pinpoint the exact time or location on the track. Nonetheless, this speed is likely to have been achieved in a transition phase as the vehicle ramped up its velocity towards 100 km/h from an earlier speed of 30 km/h.