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| = 10km, find |QR|

  • A 5.0km
  • B 7.5km
  • C 7.6km
  • D 8.7km
waec 2001mathematics

The correct answer is D. 8.7km

\((PR)^2 = (PQ)^2 + (QR)^2\)

\(10^2 = 5^2 + (QR)^2\)

\((QR)^2 = 100 - 25\)

\(QR = \sqrt{75}\)

= \(8.660\)

\(\approxeq\) 8.7 km

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