What is the length of the greatest rod that can be placed in a hall 12 m long, 4 m broad and 3 m high?

Correct option is B

Given:
Length of the hall (L) = 12 m
Breadth of the hall (B) = 4 m
Height of the hall (H) = 3 m
Concept Used:
The greatest rod that can be placed in the hall is the length of the diagonal of the cuboid (hall). The formula to find the diagonal (D) of a cuboid is given by:

$$D = \sqrt{(L^2 + B^2 + H^2)}$$  

Solution:

$$D = \sqrt{(12^2 + 4^2 + 3^2)}\\ = \sqrt{(144 + 16 + 9)}\\ = \sqrt{169}\\ = 13 \, \text{m}\\$$​​

Therefore, the length of the greatest rod that can be placed in the hall is 13 meters

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