#### Answer

302,400 sec.

#### Work Step by Step

3 $\frac{1}{2}$ Days = sec
Use the unit fraction $\frac{24 hours}{1 days}$ to change days to hours, next use the unit fraction $\frac{60 min}{1 hour}$ to change hours to min and last use the unit fraction $\frac{60 sec}{1 min}$ to change min to sec. Notice how all the units divide out except second, which is the unit you want in the answer.
$\frac{7}{2}$ days *$\frac{24 hours}{1 days}$ * $\frac{60 min}{1 hour}$* $\frac{60 sec}{1 min}$ = 302,400 sec