For this case we must convert 21 hours to seconds!
We have that by definition, 1 hour equals 3600 seconds. Then, making a rule of three we have:
1h ------------> 3600s
21h ----------> x
Where "x" represents the number of seconds equivalent to 21 hours.
[tex]x = \frac {21 * 3600} {1} = 75600[/tex]
Thus, 21 hours represent 75600 seconds.
Answer:
75600 seconds.
