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WAEC Mathematics 2001 Question 28

Question 28

Bearings

Three observation posts P, Q and R are such that Q is due east of P and R is due north of Q. If |PQ| = 5km and |PR| = 10 km, find |QR|.

  1. A.5.0 km
  2. B.7.5 km
  3. C.7.6 km
  4. D.8.7 km
Show the answer and explanation

Answer: D (8.7 km)

Explanation

The angle at Q is 90°, so QR = √(102 − 52) = √75 ≈ 8.7 km.