You are flying on a heading of 210°T at a true airspeed (TAS) of 100 knots. The forecast wind is 100/20. What do you expect your track over the ground and ground speed to be?
1 Slide the airspeed dot down onto the horizontal line at the top of the wind grid
2 Place the wind direction (100°T) under the index by rotating the compass rose.
Note that “100/20” is shorthand for wind from 100° at 20 knots
3 Vertically down from the airspeed dot, mark a cross at the wind speed (20kts)
4 Slide the airspeed dot up to your true airspeed (105kts)
5 Place your heading (210°) under the index by rotating the compass rose
6 The cross is now indicating your groundspeed and drift:
Groundspeed = 114 knots
Drift = 9° right (starboard)
So from a heading of 210° with 9° right drift, the track is 219°
Always make sure to do some gross error checking!