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A cuboid has a diagonal of length 9cm and a square base of side 4cm. What is its height?

A cuboid has a diagonal of length 9cm and a square base of side 4cm. What is its height?
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  • A 9cm
  • B \(\sqrt{65}\)cm
  • C \(4\sqrt{2}\)cm
  • D 7cm
  • E 6.5cm
Correct Answer: Option B
Explanation:
Given a cuboid, the diagonal cuts a face of the cuboid into 2 right-angled triangles.
Hence, using the Pythagoras theorem, we have
\(9^{2} = 4^{2} + x^{2}\)
\(81 = 16 + x^{2}\)
\(x^{2} = 81 - 16 = 65\)
\(\therefore x = \sqrt{65} cm\)

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