Question

convert speed of 72km/hr into m/s and cm/s

Answer 1

= 72 x 5 /18
= 20m/s

and
in cm /s
= 72 × 100000 /3600
= 72 × 1000 / 36
= 2000 m/s

Answer 2

1km = 1000m 
1 hour = 60 minutes = 3600 seconds 

72km/hr 
= 72000m/3600s 
= 20m/s