Note: Your question inputs seem a little odd. But, I am assuming that you really mean '10km in 5 ms'.
Answer:
The Average speed = 15000 / 0.005 = 3000000 m/s
Explanation:
Average speed = Total Distance / Total time
Given
Thus,
Average speed = Total Distance / Total time
Average speed = 15000 / 0.005 = 3000000 m/s