Manhole covers are round because...

Q: Why Are Manhole Covers Round?
A: Because Manholes are round.

This question was once asked by tech companies to witness a potential candidates problem solving and cognitive skills. But in reality there is no single answer to the questions, and most could be considered the correct answer.

Here are a few correct answers:

• A circular cover can not fall through a circular opening it was designed to match, but a square or rectangular cover could, if placed at an angle. This seems to be the most popular answer I found in my research.


• Round tubes are stronger, then square tubes and with stand higher environmental pressures.


• Because holes are round.


• Circular covers do not need to be rotated to fit the opening. This reminds me of carving pumpkins and leaving a key to easily match the lid to the opening
  
• so when the cover is removed the 100lb cover can easily be rolled.
  
• Most manhole workers are round, so it only fitting the hole and thus the covers are round.


• because thats how they were always made.which is not true