WAEC - Mathematics (2001 - No. 27)
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|
5.0km
7.5km
7.6km
8.7km
Explanation
\((PR)^2 = (PQ)^2 + (QR)^2\)
\(10^2 = 5^2 + (QR)^2\)
\((QR)^2 = 100 - 25\)
\(QR = \sqrt{75}\)
= \(8.660\)
\(\approxeq\) 8.7 km
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