GMAT Math : GMAT Quantitative Reasoning

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #1 : Data Sufficiency Questions

Two of the courses from which the 106 freshmen at Jefferson Academy may choose are American literature and German. 

How many freshmen enrolled in both courses?

Statement 1: 19 freshment enrolled in German.

Statement 2: 21 freshmen enrolled in American literature.

Possible Answers:

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

BOTH statements TOGETHER are insufficient to answer the question. 

EITHER statement ALONE is sufficient to answer the question.

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

Correct answer:

BOTH statements TOGETHER are insufficient to answer the question. 

Explanation:

Assume both statements are true. If  is the number of students enrolled in both courses, we can fill in the Venn diagram for the situation with the expressions shown:

Venn_1

No further information is given in the problem, however, so there is no way to calculate .

Example Question #5 : Data Sufficiency Questions

Two of the courses from which the 98 freshmen at a high school may choose are French and Creative Writing. 

How many freshmen enrolled in neither course?

Statement 1: 10 freshmen enrolled in both courses.

Statement 2: 21 freshmen enrolled in each course.

Possible Answers:

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

BOTH statements TOGETHER are insufficient to answer the question. 

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

EITHER statement ALONE is sufficient to answer the question.

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

Correct answer:

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

Explanation:

The question asks for the number of students in the set , where  and  are the sets of students who took French and Creative Writing, respectively.

From Statement 1 alone, a Venn diagram representing this situation can be filled in as follows:

Venn_1

It is known that ; subsequently, . But no other information is given, so , the desired quantity, cannot be calculated.

From Statement 2 alone, a Venn diagram representing this situation can be filled in as follows:

Venn_1

Again, no further information can be computed.

Now assume that both statements are true. Then it follows from Statement 1 that , and it follows from Statement 2 that the desired quantity is 

.

 

Example Question #1 : Data Sufficiency Questions

Venn_1

In the above Venn diagram, universal set  represents the residents of Wayne. The sets  represent the set of all teenagers, those with an even birth month, and males, respectively.

Cary is a resident of Wayne. Is Cary a male?

Statement 1: Cary is a teenager.

Statement 2: Cary does not have an even birth month.

Possible Answers:

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

EITHER statement ALONE is sufficient to answer the question.

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

BOTH statements TOGETHER are insufficient to answer the question. 

Correct answer:

EITHER statement ALONE is sufficient to answer the question.

Explanation:

The question asks if Cary is an element of .

Assume Statement 1 alone. From the Venn diagram, it can be seen that  and  are disjoint sets. Since Cary is an element of , he cannot be an element of  - Cary is not a Male.

Assume Statement 2 alone. From the Venn diagram, it can be seen that  - that is, if Cary is an element of , then she is an element of . Restated, if Cary is a Male, then he is a Teenagers. The contrapositive also holds - if Cary is not a teenager - which is given in Statement 2 - then Cary is not a male.

Example Question #2121 : Gmat Quantitative Reasoning

Venn_1

In the above Venn diagram, universal set  represents the residents of a city. The sets  represent the set of all teenagers, even birth month, and males, respectively.

Jamie is a resident of this city. Does Jamie have an even birth month?

Statement 1: Jamie is not a male.

Statement 2: Jamie is not a teenager.

Possible Answers:

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

BOTH statements TOGETHER are insufficient to answer the question. 

EITHER statement ALONE is sufficient to answer the question.

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

Correct answer:

BOTH statements TOGETHER are insufficient to answer the question. 

Explanation:

The question is whether or not Jamie is an element of .

Assume both statements to be true. Then Jamie is an element of the set , shaded in this Venn diagram:

Venn_1

Some elements of  are elements of , but some are not, making the two statements together insufficient to answer the question of whether Jamie is an element of . Whether Jamie was born in an even month or not cannot be determined.

Example Question #12 : Dsq: Understanding Sets

Let universal set  be the set of all people. Let  represent Gina.

Let  be the set of all people who like cheddar cheese. Let  be the set of all people who like Swiss cheese. 

True or false: .

Statement 1: Gina likes cheddar cheese.

Statement 2: Gina does not like Swiss cheese.

Possible Answers:

BOTH statements TOGETHER are insufficient to answer the question. 

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

EITHER statement ALONE is sufficient to answer the question.

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

Correct answer:

EITHER statement ALONE is sufficient to answer the question.

Explanation:

 is the intersection of , the complement of the set of people who like cheddar cheese - that is, the set of people who don't like cheddar cheese - and , the set of people who like Swiss cheese. For  to be true, it must hold that Gina doesn't like cheddar cheese and Gina likes Swiss cheese. Either statement alone makes this false.

Example Question #13 : Dsq: Understanding Sets

Let universal set  be the set of all people. Let  represent Holly.

Let  be the set of people who like The Eagles, , the set of people who like Bruce Springsteen, and , the set of people who like Crosby, Stills, and Nash.

True or false: Holly likes The Eagles.

Statement 1: 

Statement 2: 

Possible Answers:

EITHER statement ALONE is sufficient to answer the question.

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

BOTH statements TOGETHER are insufficient to answer the question. 

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

Correct answer:

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

Explanation:

Assume Statement 1 alone.  is the intersection of two sets -  and , the complements of, respectively, the set of people who like The Eagles and the set of people who like Bruce Springsteen. Equivalently, this is the intersection of the set of people who do not like The Eagles and the set of people who do not like Bruce Springsteen. Since , Holly falls in both sets. Specifically, she does not like The Eagles.

Assume Statement 2 alone.  is the union of two sets - , the set of people who do not like The Eagles and , the set of people who like Crosby, Stills, and Nash. If , Holly falls in either or both sets, so either she doesn't like The Eagles, or she likes Crosby, Stills, and Nash, or both. It is not resolved whether she likes The Eagles or not.

Example Question #12 : Word Problems

Let universal set  be the set of all people. Let  represent Veronica. 

Let  be the set of people who like Pearl Jam, , the set of people who like Nirvana, and , the set of people who like Soundgarden.

True or false: Veronica likes at least two of Pearl Jam, Nirvana, and Soundgarden.

Statement 1: 

Statement 2: 

Possible Answers:

EITHER statement ALONE is sufficient to answer the question.

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

BOTH statements TOGETHER are insufficient to answer the question.

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

Correct answer:

BOTH statements TOGETHER are insufficient to answer the question.

Explanation:

Assume both statements to be true.

 is the union of the sets , and ; Veronica falls in this union, so she falls in at least one of the three sets, so she likes one, two, or all three of Pearl Jam, Nirvana, and Soundgarden.

Similarly, from Statement 2, Veronica falls in at least one of the three sets , and  - the complements of the three sets - meaning that she doesn't like at least one of the three. Therefore, Veronica likes none, one, or two of the artists.

From the two statements together, it follows that Veronica likes one or two of the artists. Without further information, however, it cannot be determined whether she likes two of the artists.

Example Question #15 : Dsq: Understanding Sets

Let universal set  be the set of all people. Let  represent Frank.

Let  be the set of all people who like tea. Let  be the set of all people who like coffee.

True or false: .

Statement 1: Frank likes tea.

Statement 2: Frank likes coffee.

Possible Answers:

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

EITHER statement ALONE is sufficient to answer the question.

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

BOTH statements TOGETHER are insufficient to answer the question. 

Correct answer:

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

Explanation:

 is the union of the set , the set of all people who like coffee, and , the complement of the set of all people who like tea - that is, the set of all people who do not like tea.  if either Frank likes coffee or Frank does not like tea or both

Statement 1 alone, that Frank likes tea, does not prove or disprove this to be true true; if Frank likes coffee, then this is true, and if he does not like coffee, then this is not true. Statement 2 alone, however, proves this statement true.

Example Question #13 : Word Problems

Every Bee is a Cee. Every Dee is a Cee. Every Cee is a Fee.

True or false: Bumpy is a Fee.

Statement 1: Bumpy is not a Dee.

Statement 2: Bumpy is not a Bee.

Possible Answers:

EITHER statement ALONE is sufficient to answer the question.

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

BOTH statements TOGETHER are insufficient to answer the question.

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

Correct answer:

BOTH statements TOGETHER are insufficient to answer the question.

Explanation:

 and .

This can be respresented in a Venn diagram as follows:

Venn 2

Assume both statements to be true. If we let  represent Bumpy, then from the diagram, it can be seen that if Bumpy is neither a Bee or a Dee, it is possible for Bumpy to be be a Fee or to not be a Fee.

Example Question #14 : Word Problems

No Fee is a Fi. No Fi is a Fo. No Fo is a Fum. 

True or false: Jack is a Fum.

Statement 1: Jack is not a Fo.

Statement 2: Jack is not a Fi.

Possible Answers:

EITHER statement ALONE is sufficient to answer the question.

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

BOTH statements TOGETHER are insufficient to answer the question.

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

Correct answer:

BOTH statements TOGETHER are insufficient to answer the question.

Explanation:

Let  be the sets of Fe's, Fi's, Fo's and Fum's, respectively. According to the premise of the problem, the sets  and  are disjoint (they have no elements in common); the sets  and  are disjoint; and the sets  and  are disjoint. No other relationships are known. A Venn diagram of these relationships is below:

Venn 2

Assume both statements to be true. The question is whether or not Jack falls in set . If Jack is neither a Fi nor a Fo, then Jack falls in neither set  nor set . As evidenced by the two X's in the diagram, it is possible for Jack to fall in set  or to not fall in set . Therefore, the question of whether Jack is a Fum is unresolved.

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