Let the usual speed of the plane be x km/hr.Usual time taken by train =x1500​After increase in speed time taken =x+1001500​Then according to question,​∴x1500​−x+1001500​=6030​⇒x2+100x−300000=0⇒x2+600x−500x−300000=0⇒(x+600)(x−500)=0x=−600,∴x=500​Speed of plane =500 km/hr