What is the length of the longest pole that can fit itself in a hall…

Length of diagonal of a cuboid = Length of the longest chord =\(\sqrt {l^2 + b^2 + h^2}\)

Here, hall has length = 60 feet ,

breadth = 30 feet

height = 20 feet 

So, length of the longest rod = \(\sqrt {60^2 + 30^2 + 20^2}\)= \(\sqrt {4900}\) = 70 feet