1. What was Henk Angenent's record?
- He finished the race in 6 hours and 49 minutes.
2. What was Henk Angenent's record?
- His record was 6 hours and 49 minutes.
(Are both answers right?)
3. In 1963, how many percent of the skaters finished the race?
- Only one percent of the skaters finished the race.
(Is the question grammatical? Can we use other questions suitable for the answer?)
1 and 2 are both correct, yes.
For 3, here are two ways the question can be phrased:
In 1963, what percentage of the skaters finished the race?
or
In 1963, how many skaters finished the race?
The answer to both questions can be what you have written.