In set notation this is B = {1, 4, 9}. 30 people answered a survey about whether they have a dog or a cat. The Venn diagram shows the information from the survey. 13 people have got a dog.

Although Venn diagrams initially applied to logic and set theory, the four-circle conundrum raised an interesting geometry question. That seed has blossomed into a fascinating investigation into ...

Now Khalegh Mamakani and Frank Ruskey at the University of Victoria in British Columbia, Canada, have hit on the first simple, symmetric 11-set Venn diagram (pictured). One of the sets is outlined ...

Venn diagrams get tricky when they include more than three sets – here, a fourth set has to be stretched across the other three. (Image: Kopophex/Wikimedia Commons) The stretching method starts ...