I am trying to find all the solutions and put them together at a single place, So feel free to add comments and if you have a solution please do post. Cheers … 🙂
Here is the puzzles link : http://www.wuriddles.com/
Question : Why are manholes round?
Note: This is a famous Microsoft question. Yet amusingly, the Microsoft campus uses square manholes.
My Solution : I guess there are 2 basic reasons for this. The first one is that, the cover cant get inside the manhole whatever we do. But a square manhole can pass through the man hole by putting it diagonally. And the second one is carrying it is very easy. We can roll over the cover from one place to other easily, where as in the square manhole, its not possible……. 🙂