Answer
518,400 sec.
Work Step by Step
6 days = sec
Use the unit fraction$\frac{24 hours}{1 day}$ to change days to hours, next use the unit fraction $\frac{60 min}{1 hr}$ to change hours to min and last use the unit fraction $\frac{60 sec}{ 1min}$ to change min to sec. Notice how all the units divide out except second, which is the unit you want in the answer.
6 days * $\frac{24 hours}{1 day}$ * $\frac{60 min}{1 hr}$*$\frac{60 sec}{ 1min}$ = 518,400 sec.
