An aircraft departs points A (50°N, 012°E) on a westerly track and flies for 300 NM to point B. From point B, the aircraft flies a southerly track of 300 NM to point C. From point C, the aircraft finally flies a westerly track of 300 NM to point D. The coordinates of point D are:
To solve this type of question, it is important to be familiar with:

Departure (NM) = Change of Longitude (min) x 60 x cos Lat

One minute of latitude equals one nautical mile and degrees of latitude are 60 nm apart.
(1) From 50ºN 012ºE => Aircraft flies westwards for 300 NM
Start by using the Departure formula to find the change of longitude:
300 NM = Change of longitude (min) x 60 x cos (50º)
Change of longitude (º) = 300 / [cos (50º) x 60] = 7.78 (Convert it to minutes)
Change of longitude (º) = 7.47º westerly
 After the first leg (westwards), the aircraft will be at 012ºE  007.47º = 4.13º E

50ºN 004.13ºE
(2) From 50ºN 003.7ºE => Aircraft flies southwards for 300 NM
1º Latitude = 60 NM
Therefore, 300 NM / 60 NM = 5º southerly
 After the second leg (southwards), the aircraft will be at 50ºN  5ºS = 45ºN

45ºN 004.13ºE
(3) From 45ºN 003.7ºE => Aircraft flies westwards for 300 NM
Start by using the Departure formula to find the change of longitude:
300 NM = Change of longitude (min) x 60 x cos (45º)
Change of longitude (º) = 300 / [cos (45º) x 60] = 7.07 (Convert it to minutes)
Change of longitude (º) = 7.04º westerly
 After the third leg (westwards), the aircraft will be at 004.13ºE – 7.04º = 2.51ºW

45ºN 002º51’W
=> Aircraft's final position: 45ºN 002º51’W
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