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JAMB Mathematics 1985 Question 46

Question 46

Latitude and Longitude

Two points X and Y both on latitude 60°S have longitudes 147°E and 153°W respectively. Find to the nearest kilometre the distance between X and Y measured along the parallel of latitude. (Take 2πR = 4 × 104km, where R is the radius of the earth).

  1. A.28,850km
  2. B.16,667km
  3. C.8,333km
  4. D.6,667km
  5. E.3,333km.
Show the answer and explanation

Answer: E (3,333km.)

Explanation

Going across the 180° line, the angle between 147°E and 153°W is 33° + 27° = 60°. The parallel at 60° has length 2πR cos 60° = 20 000km, so the distance is 60/360 × 20 000 ≈ 3,333km.