<PRE><B>Question 965986</B>
 speed of a plane = 180 m/s = 180* 18/5
                            = 648 km/h 
  ( to convert m/s to km/h we should multiply by 18/5)
 
 now
 to travel 648 km the time taken by a plane = 1 h
 to travel 800 km the time taken by a plane = 1/648 *800
                                           = 1 h 19 min
                                           = 79 min
hence solved</PRE>