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An aeroplane is circling the Earth following parallel of latitude 60°N at a ground speed of 480 kt. To circle the Earth along the equator in the same amount of time, it should fly at a ground speed of…
  • A
    550 kt.
  • B
    240 kt.
  • C
    480 kt.
  • D
    960 kt.

We need to find the actual distance of the 60 ° N parallel to the Earth:There is a total of 360 Long and each 60 ’= 360 x 60 = 21600 min

Distance = Change in Long (in minutes) x cos Lat
Distance = 21600 x cos 60 ° = 10800 NM

How long does it take at 480 kt to cover 43200 NM:
Correct proportion => x MIN = (60 * 10800) / 480 = 1350 MIN

Among the parallels only 1 ° = (60 ’) on the Equator equals 60 NM:
Total Distance of Equator on Earth = 360 x 60 = 21600 NM

The question is how fast it takes to fly the entire equator at the same time:
Correct proportion => x kt = (60 * 21600) / 1350 = 960 kt

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