To calculate the average speed of the car, we can use the formula:
Average speed = Total distance / Total time
Let's assume the distance between Lahore and Islamabad is "D."
For the first part of the journey, when the car travels from Lahore to Islamabad at a speed of 100 m/s, the time taken would be:
Time = Distance / Speed = D / 100
For the return journey, when the car travels from Islamabad to Lahore at a speed of 200 m/s, the time taken would be:
Time = Distance / Speed = D / 200
The total time for the round trip would be the sum of these two times:
Total time = D / 100 + D / 200 = (2D + D) / 200 = 3D / 200
The total distance traveled for the round trip is 2D (going from Lahore to Islamabad and then back).
Now, we can calculate the average speed:
Average speed = Total distance / Total time = 2D / (3D / 200) = 400/3 m/s ≈ 133.33 m/s
Therefore, the average speed of the car for the round trip is approximately 133.33 m/s.