Q: The pilot of an aircraft flies due east relative to the ground in a wind blowing 20 km/h toward the south. If the speed of the aircraft in the absence of wind is 70 km/h, what is the speed of the aircraft relative to the ground? I set up the vector of wind WRT ground pointing due south, then the vector of the plane WRT the ground extending due E from the tail of the first, so the resultant vector is the plane WRT the wind. I tried solving this my just using the pythagorean theorem bc of the presence of a right angle, but was terribly wrong. Can someone point me in the right direction, I'm just totally stumped on this one, thanks!