GRE Math : GRE Quantitative Reasoning

Study concepts, example questions & explanations for GRE Math

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Example Questions

Example Question #441 : Gre Quantitative Reasoning

, solve for .

Possible Answers:

Correct answer:

Explanation:

The first step is to multiple each side by  and that leaves you with 

.  

The next step will be to add  to both sides resulting in 

.  

Finally divide both sides by  giving answer of .

Example Question #1071 : Algebra

For which value of  are the following two functions equal?

  

Possible Answers:

5

4

3

2

6

Correct answer:

4

Explanation:

It is important to follow the order of operations for this equation and find a solution that satisfies both F(x) and G(x).

Recall the order of operations is PEMDAS: Parentheses, Exponents, Multiplication/Division, Addition/Subtraction.

The correct answer is 4 because 

F(x) = 2x + 3+ (9x/3) = 2(4) + 34 + ((9 * 4)/3) = 101, and

G(x) = (((24 + 44)/2) - 4 * 4) – 5(4) + 1 = 101.  

 

 

 

Example Question #441 : Gre Quantitative Reasoning

The function  is defined as . What is  ?

Possible Answers:

24

-36

56

18

36

Correct answer:

24

Explanation:

Substitute -1 for  in the given function.

If you didn’t remember the negative sign, you will have calculated 36. If you remembered the negative sign at the very last step, you will have calculated -36; however, if you did not remember that  is 1, then you will have calculated 18.

Example Question #442 : Gre Quantitative Reasoning

If the function  is created by shifting  up four units and then reflecting it across the x-axis, which of the following represents  in terms of ?

Possible Answers:

Correct answer:

Explanation:

We can take each of the listed transformations of  one at a time. If  is to be shifted up by four units, increase every value of  by 4. 

Next, take this equation and reflect it across the x-axis. If we reflect a function across the x-axis, then all of its values will be multiplied by negative one. So,  can be written in the following way:

Lastly, distribute the negative sign to arrive at the final answer.

Example Question #1 : How To Find The Intersection Of A Venn Diagram

In a class, there are 15 students who like chocolate. 13 students like vanilla. 10 students like neither. If there are 35 people in the class, how many students like chocolate and vanilla?

Possible Answers:

25

13

3

10

2

Correct answer:

3

Explanation:

In order to find the intersection of chocolate and vanilla, it is easiest to make a Venn Diagram. The outside of the Venn Diagram is 10, and the total of the entire diagram must equal 35. Therefore the two circles of the Venn Diagram including just chocolate, just vanilla and the intersection must equal 25, with the just chocolate plus intersection side equalling 15 and the just vanilla plus intersection side equalling 13.

We know:

(A U B) = A + B – (A ∩ B)

We have found that (A U B) = 25 and we are trying to find (A ∩ B). Plug in A and B

25 = 15 + 13 – (A ∩ B) = 28 – (A ∩ B)

or – (A ∩ B) = –3 

(A ∩ B) = 3

Example Question #1 : Data Analysis

A given company has 1500 employees. Of those employees, 800 are computer science majors. 25% of those computer science majors are also mathematics majors. That group of computer science/math dual majors makes up one third of the total mathematics majors. How many employees have majors other than computer science and mathematics?

Possible Answers:

None of the other answers.

Correct answer:

Explanation:

Refer to the following Venn Diagram:

 Csmathvenn

If 25% of the 800 CS students are also mathematics students, the number of students sharing these majors is 800 * 0.25 or 200 students. Furthermore, if this represents one third of the total of math students, we then know:

Math students * 1/3 = 200 or (1/3)M = 200

Solving for M we get 600.  This means that the number of students that are ONLY math students is 400.

Looking at our diagram above, we must be careful not to "double add" the intersection. The easiest way to do this is to take the intersection and add to it the number of CS-only and math-only students: 600 + 200 + 400 = 1200.  This number represents the total number of students that have either a math or CS major (that is, the number of students in the union of the two sets). This leaves 1500 – 1200 or 300 students.

Example Question #3 : How To Find The Intersection Of A Venn Diagram

In a population of cats, 10% are tabby colored, 5% are pregnant, and 3% are both tabby and pregnant. What is the probability that a cat is tabby but not pregnant?

Possible Answers:

Correct answer:

Explanation:

Probability (tabby but not pregnant)

= Prob (tabby) – Prob (tabby and pregnant)

= 10% - 3%

= 7%

Example Question #1 : How To Find The Intersection Of A Venn Diagram

At an overpriced department store there are  customers. If  have purchased shirts,  have purchased pants, and  have purchased neither, how many purchased both shirts and pants?

Possible Answers:

Correct answer:

Explanation:

A way of solving this problem is by drawing a Venn diagram based on what is known:

Venndiagram

There are  customers; within them there are those that purchased something (pants, shirts, or possibly a combination), and those that purchased nothing.

The amount of individuals that purchased something is given as:

The reason that the number of shoppers that bought both is subtracted is so that it is not counted twice when the customers that bought pants and the customers that bought shirts are added together.

Since  bought nothing,

The amount that bought both then is:

Example Question #1 : How To Find The Intersection Of A Venn Diagram

In a school, 70 students are taking classes. 35 of them will be taking Accounting and 20 of them will be taking Economics. 7 of them are taking both of these classes. How many of the students are not in either class?

Possible Answers:

Correct answer:

Explanation:

When you add both class rosters you get a total of 55 students 

.

You must subtract the 7 that are in both because they are counted twice in the 55 

.  

The total in neither class will be the total students minus the adjusted enrollment in both classes 

.

Example Question #1 : Data Analysis

There are 15,000 students at college X.  Of those students, 1,700 are taking both ethics and metaphysics this semester.  There are 2,200 total students taking ethics.  9,500 students are taking neither of these classes.  How many students are taking metaphysics this term?

Possible Answers:

5,000

None of the other answers.

1600

3300

3800

Correct answer:

5,000

Explanation:

The easiest way to understand this problem is to draw a Venn Diagram:

Ts4vennphilclass

S = Total number of students

A = Total students taking ethics

B = Total students taking metaphysics

A - B = Students taking only ethics

B - A = Students taking only metaphysics

A ∪ B = The total students taking either ethics or metaphysics

A ∩ B = The total students taking both ethics and metaphysics

 

We know there are 15,000 total and that 9,500 are taking neither class.  Therefore, we know that 15,000 - 9,500 = 5,500 are taking at least one of the classes.  Based on our prompt, we know that there are 1,700 taking both and that 2,200 are taking ethics.  To fiind out how many are taking ONLY ethics, we have to subtract off the amount that are taking ethics and metaphysics.  Hence, 2,200 - 1,700 = 500.  Finally, if we know that there are 5,500 taking at at least one of these classes, we want to get rid of that portion taking ethics.  This will leave us with those who are taking at least metaphysics (regardless of whether or not they are taking ethics): 5,500 - 500 = 5,000.

 

 

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