Final answer:
The average speed required for the last two laps, calculated based on the distance and time equations, must be 485.71 km/hr, which was not listed among the provided options.
Step-by-step explanation:
To find out the average speed the race car driver must maintain over the last two laps, we first need to calculate the total distance the driver needs to cover in all four laps.
Let's assume the length of one lap is L kilometers. Therefore, the total distance for four laps is 4L kilometers. The target average speed is 200 km/hr, so the total time needed for the four laps at the target speed is 4L/200 hours.
However, due to engine trouble, the car averages only 170 km/hr for the first two laps, covering a distance of 2L kilometers. This takes 2L/170 hours.
The time left for the remaining two laps is the total time minus the time already spent: 4L/200 - 2L/170 hours.
The remaining distance to cover is 2L kilometers. We need to find the required speed, V, to cover this distance in the remaining time. The average speed equation is:
Substituting in the remaining distance and time, we get:
- V = 2L / (4L/200 - 2L/170)
By solving this equation, we can find the required average speed V for the last two laps.
After simplifying, we get:
- V = 200 * 170 / (170 - 100)
- V = 34000 / 70
- V = 485.71 km/hr
Thus, the correct answer is not among the provided options (a, b, c, d). The driver must average 485.71 km/hr over the last two laps.