What is an expmple of a venn diagram?

Answer 1

A Venn diagram (named after the mathematician Venn) is usually a rectangle with 2 or 3 overlapping cicles drawn inside it. They don't have to be perfect cicles; just loops will do. Now suppose that we are talking about "All 400 pupils in a school"; they have to be shown somewhere in the rectangle, which represents the 400 pupils. Now, speaking about the subjects Mathematics, Geography and Chemistry we draw 3 loops overlapping each other, labelling one M for Maths, another G for Geog and the third C for Chem. Where M and G overlap we have to place the number of pupils who take both Maths and Geog;, but some of them might take Chem as well and some will not. Similarly there will be pupils who take Maths and Chem, of which some will take Geog and some will not. Then there are those who take Geog and Chem of which some may take Maths and some may not. There are two other groups too; those who don't take any of those 3 subjects, and some who take all 3 of them.

Now put onto the various regions of the diagram the numbers of pupils as follows: 50 take only Maths; 60 take only Geog; 35 take only Chem; 40 take M and G but not C; 30 take G and C but not M;20 take M and C but not G; 100 take none of those subjects.

Now for the stinker: "How many take all 3 subjects?"