b) do we need to convert velocity of sound wave given in cm/s to m,/s ?????

yes it will be easy for the attempter to convert cm/s into m/s as all velocity of sound are given in m/s 
for example, Granite=6000 m/s 
  and rest according to ques given.

  • 1
Yes ,because m/s is the standard unit of velocity.
  • 2
What are you looking for?