Castle - solution
You can put one foot-bridge over one corner (thus a triangle is created). Then from the middle of this foot-bridge lay another foot-bridge to the edge (corner) of the castle. You can make a few easy equations confirming that this is enough.
going of what the soultion claims... does he mean 1 ft, or 1M?
or, does he say 1 ft to imply 1/3 M?
thats why i started saying 'unit length' as opposed to M or ft