<PRE><B>Question 640335</B>
let the speed of the plane in still air =x
and the speed of the wind=y
flying with the wind travels 540 km in 2 hours
so 2[x+y]=540 
or x+y=270  ----1
 Later, flying against the same wind, the plane travels 690 km in 3 hours
so 3[x-y]=690
  or x-y=230   ---------2
adding 1   &amp; 2
2x=500 or x=250 km/hr =speed of aeroplane
from 1 y=270-250=20 km/hr = speed of air
ans</PRE>