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JAMB Mathematics 1992 Question 27

Question 27

Latitude and Longitude

Determine the distance on the earth's surface between two towns P(Lat. 60°N, Long. 20°E) and Q(Lat. 60°N, Long. 25°W) (Radius of the earth = 6400km)

  1. A.800π/9 km
  2. B.800√3π/9 km
  3. C.800πkm
  4. D.800√3πkm
Show the answer and explanation

Answer: C (800πkm)

Explanation

The longitude difference is 20° + 25° = 45°. The radius of latitude 60° is 6400 cos 60° = 3200km. Distance = 45/360 × 2π × 3200 = 800πkm.