Q83
ReasoningVenn Diagrams & Set Theory
Choose the correct diagram to represent books, Bengali books and novels. [The options are Venn diagrams, described here in words.]
- a.Two separate small circles placed inside one large closed curve
- b.One large circle with two small circles, each cutting across its boundary on opposite sides
- c.One large circle with one small circle fully inside it and another small circle cutting across its boundary
- d.One large circle containing two small circles that overlap each other
Answer: (D) One large circle containing two small circles that overlap each other
"Books" is the widest class, so it is the large circle. Every Bengali book is a book and every novel is a book, so both small circles must lie wholly inside the large one. Some Bengali books are novels (and some novels are Bengali books), so the two small circles must overlap each other. Only the last diagram shows this. The first diagram would suit two unrelated sub-classes such as "books, novels, dictionaries"; the diagrams in which a small circle crosses the boundary of the large one would wrongly mean that some Bengali books or novels are not books.