An observer standing at station observes frequency 219 Hz when a train approaches and 184 Hz when train goes away from him. If velocity of sound in air is 340 m/s, then velocity of train and actual frequency of whistle will be

When train is approaching frequency heard by the observer is na=n vv−vS⇒219=n 340340−vS         …(i)when train is receding (goes away), frequency heard by the observer is nr=n vv+vs⇒184=n340340+vs         …(ii)On solving equation (i) and (ii) we get  n=200 Hzand  vS=29.5 m/s.