The length and breadth of a room are 21 m and 16 m respectively. If the length of the longest rod that can be placed in the room is 29 m, then what is the height of the room?

  1. A. 10 m
  2. B. 11 m
  3. C. 12 m
  4. D. 13 m

Correct Answer: C. 12 m

Explanation

The longest rod corresponds to the body diagonal of the cuboidal room: d = \sqrt{l^2 + b^2 + h^2}. We have 29 = \sqrt{21^2 + 16^2 + h^2} \implies 841 = 441 + 256 + h^2 \implies 841 = 697 + h^2 \implies h^2 = 144 \implies h = 12\text{ m}.

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