You are here: Home Activities Maths on the DART Red Poster, Question 1

Red Poster, Question 1

Why are most manhole covers circular?


After I wrote this question I started to notice a lot more square manhole covers. Also there are probably lot’s of good reasons for having round covers. So, the question perhaps should be “what is the big advantage in having a round manhole cover?”

The answer is that a round manhole cover can’t fall into a round manhole – whatever way you turn it. This is a big advantage I’m sure you’ll agree. Whereas a square manhole cover can fit easily into a square hole if aligned along the diagonal of the hole.