A man returns home from a two month trip and discovers that his enemies have put a moat around his property. The property consists of a 108×108 foot square centered within a 140×140 foot square, and everything between the two is water. No boat is available and he cannot swim. His only hope is two sturdy planks left behind by the construction crew. Each plank is sixteen feet long, so they are too short to span the moat. He has no way to tie them together. How does he get across?
I do not fully understand this question.
Why 16 ft flank "too short to span the moat" ?
Can anyone explain this and give me some ideas?