Question

the length of the longest flag pole that can be put in a storeroom of dimensions 10m ×10m ×5m is

Answer 1

the longest length is the diagonal of the room.
therefore length of the pole is 15m.

Answer 2

on cuboid the longest length inside any cuboid can be given by formula
$\sqrt{ {length}^{2} + {breadth}^{2} + {height}^{2} }$
which becomes
√[(10)^2 + (10)^2 + (5)^2]
√[225]
15cm