Answer:
0.6 km/sec
Explanation:
72 km/hr divided by 60 mins/hr = 1.2 km/min
the hrs cancel each other out, leaving km/min
1.2 km/min divided by 60 sec/min = 0.02 km/sec
the mins cancel each other out, leaving km/sec
0.02 km/sec * 30 sec = 0.6 km
the secs cancel each other out, leaving only the km, which is your answer.