Studying NAV at the moment and im taking my test tomorrow. This is how you do it.
"if you wish to maintain a groundspeed of 80kts on track calculate the true heading and TAS required if wind velocity is 090/20 true and track is 180 degress true?"
Put differently. - Given a W/V of 09020kt and a track of 180T, what heading and TAS should be flown to maintain a ground speed of 80kts on track.
On your whizzwheel first you need to set your black dot to 090 and 20 knots on a spot of best convenience (100 is a good spot). Mark 20 knots from the black dot. 100 - 20 = 80 so make a mark at 80 knots. Now we need to rotate it to a track of 180T. So we want to maintain a speed of 80kts so we need to slide our wheel till our mark is on 80kts. (the mark we made)
Next we need to correct for drift... it's 12 knots to the starboard side, so we need to correct it by spinning to the right, it sits at 12 drift, giving us a new heading and velocity.
165T and 75kts
This is how the test will want you to do it, and it will get you the mark, theres no reason to go too far into things, at the end of the day, if it gets you a mark then that's what you need to pass.