Answer:
90%
Explanation:
The total length of the trip was 500 miles.
Josiah fell asleep after they had traveled 450 miles.
We need to find what percent of 500 miles is 450 miles.
To do that, we divide 450 by 500 and multiply by 100:
= 90%
They had traveled 90% of the total trip when Josiah fell asleep.