When Microsoft was recruiting, there was a famous question: Why are sewer lids round? Try how many you can search for

This is very simple,

1. From a mathematical point of view, the circle has the largest area with the same perimeter

2. From the use of From a perspective, you can’t throw a round sewer cover into the sewer, but a square cover is very easy

3. Because if you look at it, among our common items , Large round iron covers are rare, so scrap stations will also pay attention to them when purchasing, and square iron plates are everywhere

4. The sewer opening is round