Answer:
The runner's time to complete the marathon was 90% of the time to complete the last marathon.
Explanation:
Given that the runner's time to complete the marathon was 10% less than the time to complete the last marathon.
The amount of time the runner needed this time as compared to the last marathon= 100% - 10%=90%
Hence, the runner's time to complete the marathon was 90% of the time to complete the last marathon.