The length of the longest rod that can be placed in a room of dimensions 10 m × 10 m × 5 m is :

Answer: Option B

Required length :
$$\begin{array}{rl}& =\sqrt{{\left(10\right)}^2+{\left(10\right)}^2+{\left(5\right)}^2}m\\ & =\sqrt{225}m\\ & =15m\end{array}$$