What is the length of the longest pole that can fit itself in a hall 60 feet long, 30 feet broad and 20 feet high?

70 feet

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

Where,

 l= length ,

b= breadth

h = height

 Here, hall has length = 60 feet ,

breadth = 30 feet and

height = 20 feet 

As, the length of the longest rod that can be placed in a room is it's diagonal 

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

= \(\sqrt {(4900 }\)) = 70 feet