posted by Matt .
A cessna plane flies with a speed of 150km/h relative to the air and points due east. A wind is blowing at a speed of 20km/h at 45 degrees south of east (ie the wind is blowing from the northwest). The resultant veloity of the plane relative to the ground is?
It is the vector sum of the wind velocity vector and the velocity of the plane with respect to the air.
You should be able to perform this operation yourself