Mentor: If I have two sets of numbers, is it possible for the
sets to have
elements in common? Can an element be in both sets?
Student 1: Well... 5 is an odd number, and it's also a
Mentor: Great! So, elements can be part of two sets at once. I'm going to draw a picture to represent
that, and you all can help me put some elements in the correct place.
Mentor: I put 5 in the place where these two circles overlap. Why do you think that I did that?
Student 2: Well, it's a prime number and an odd number, so the way you drew it, it's clear that it is a
part of both circles!
Mentor: So what should we call those circles?
Student 2: They are sets, aren't they?
Mentor: Wonderful! Can anyone think of another number that I could put in this diagram? What about a
number that is odd, but that isn't prime?
Student 3: You could put the number nine in the odd number circle, but not in the prime number circle,
because it's divisible by 3.
Mentor: Perfect answer! What we are making here is called a
Venn Diagram. Sometimes they have two circles, like the one we have drawn here, and sometimes they have
more! Let's put a few more elements in this one, then we can try to create a Venn diagram with
Continue to allow students to suggest elements until you feel they understand Venn diagrams.