Question 855167
There are 60 seconds in a minute, and 60 minutes in an hour.  That's 3600 seconds in an hour.  72/3600 = .02km/sec.<P>
km/hr * hr/min * min/sec = km/sec.  km/hr * 1 hr / 60 min * 1 min . 60 sec = km/sec = km/hour * 1/60 * 1/160 = km/hr / 3600.