13 feet
Pythagorus is used
25 + 144 = 169
169 is 13 to the second power etc
First you'd convert the seconds into minutes by dividing.
18,000 / 60 (60 secs in a min) = 300 minutes
Then, similarly, you would convert the minutes into hours.
300 / 60 (60 mins in an hr) = 5 hours
The answer is 5 hours.