GMAT Quant: Sets and Venn Diagrams

The GMAT quant: Sets and Venn Diagrams is one of the most common topics you would come across in the quantitative section of the exam. If you practice these questions well enough, they aren’t that difficult to answer. So, let’s understand this topic further. 

Sets are the most fundamental concepts of mathematics. It is a collection of elements or objects. If the members of the sets are just numbers, then the {} set notation is used. Such as, R = {1, 2, 3, 4, 5, 6, 7, 8}; where R is the set that contains eight members that are numbers.

The most often tested topic from the Sets section of GMAT is overlapping sets. An overlapping set is a set that shares its boundaries with two or more different sets. The simplest form of overlapping set is a Venn diagram, depicting two overlapping circles.

When two sets share some common properties, these properties are said to be overlapping.

Set operations:

Intersection of Two Sets:

X Y

Overlapping of Two Sets:

A B

Sets and Venn Diagrams Questions

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Sets and Venn Diagrams Solutions

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Sample Questions: 

Question 1: Out of forty students, 14 are taking English composition and 29 are taking Chemistry. How many students are in either class?

1. Maximum of 10 students out of 40 can take both classes.
2. 5 students are in both classes.

Decide whether the data given are sufficient for answering the question and then indicate one of the following answer choices:

1. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
2. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
3. BOTH statements TOGETHER are sufficient, but neither statement ALONE is sufficient.
4. EACH statement ALONE is sufficient.
5. Statement (1) and (2) TOGETHER are not sufficient.

Solution:

Statement (1): Given; a maximum of 10 students out of 40 can take both classes, but to find the number of students who are in neither class, we need to know the exact number of students taking both classes.

NOT sufficient.

Statement (2): 5 students are in both classes.

So, number of students who are in neither classes = 40-14-29+5 = 2

Sufficient.

Answer B.

Question 2: Many of the students at Oxford University speak English or German or both. Among the students who speak English, four times as many speak German as don’t. In addition, 1/6 of the students who don’t speak German do speak English. What fraction of the students speak German?

1. Exactly 60 students speak English and German.
2. Exactly 75 students speak neither English nor German.

Decide whether the data given are sufficient for answering the question and then indicate one of the following answer choices:

1. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
2. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
3. BOTH statements TOGETHER are sufficient, but neither statement ALONE is sufficient.
4. EACH statement ALONE is sufficient.
5. Statement (1) and (2) TOGETHER are not sufficient.

Solution:

	English	No English
German	4x		(?)
No German	X	5x	6x
	6x

Statement 1:- 4x = 60

x = 15

So, the number of students speaking German = 180+60 = 240

No. of students not speaking German = 6

NOT sufficient.

Statement 1 and 2:- Using both statements together also we can get only x = 15 and not the total fraction of students who speak German.

Not sufficient.

Correct answer is option (E).

The Sets and Venn Diagrams chapter in the GMAT exam is one of the most commonly tested in the actual examination. It is important to pay attention to this topic as the odds that you will be tested on it are extremely high. Moreover, it is an integral part of basic mathematics, and you will use it in one way or another, both in the examination and in your MBA program itself.