Longest rod and shortest ant path in a box

Longest rod and shortest ant path in a box

IP 2
7 marks

A closed box is a cuboid measuring \(30\) cm by \(40\) cm by \(120\) cm. \(P\) and \(Q\) are opposite corners of the box.

  1. Find the length of the longest straight thin rod that fits inside the box.[2]
  2. An ant walks from \(P\) to \(Q\) along the outside surface of the box. By unfolding two faces into a flat net, find the length of the shortest possible path, giving your answer correct to \(3\) significant figures. Explain why there are three paths to compare.[5]

Solution:

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Answer:(a) \(130\text{ cm}\) (b) \(139\text{ cm}\) (3 s.f.); the crossed edge can be any of the three edge directions, giving \(\sqrt{19300}\), \(\sqrt{24100}\), \(\sqrt{26500}\)

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