For questions relevant to the general or subject-specific Graduate Record Examination, abbreviated GRE.

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6
votes
1answer
57 views

Is this GRE math problem wrong?

I'm working out of the Manhattan GRE test prep book and I've come across a question that I can't figure out why they chose the answer they did. "Perpendicular lines m and n intersect at point (a,b), ...
0
votes
2answers
24 views

Incomplete Question? - Ratio

I have encountered the following question in the famous "5LB book of GRE" book If the zoo currently has 80 total birds, what is the samllest number of birds that could be added such that atleast 20% ...
0
votes
2answers
27 views

Simple Ratio Question - What is wrong with my approach?

A zoo has twice as many zebras as lions and four times as many monkeys as zebras Their total is a multiple of ? (The answer is 11 but my solution gets me 13) Here is how I'm solving it: Z=2(L) -> ...
-1
votes
1answer
21 views

If A/B gives __ of 3, then B must be at least 4

I had an old note that I quickly wrote and I'm really unable to read the word after 'gives'. Can someone help me out? "If A/B gives __ of 3, then B must be at least 4"
0
votes
1answer
36 views

Probabilites, Statistics and Counting Questions

I'm practicing some GRE math problems which I don't have answers for. Would you please correct my answers if they're wrong? Q1. You have 4 books, A and B and C and D. In how many ways you can ...
2
votes
2answers
53 views

Derived subsets and topological spaces

My question is regarding question $56$ from this GRE practice exam [PDF]: For a subset $S$ of a topological space $X$, let $\operatorname{cl}(S)$ denote the closure of $S$ in $X$, and let ...
3
votes
3answers
269 views

Algebra question from practice GRE exam

The following is a question from the GRE exam GR9367: Let $n > 1$ be an integer. Which of the following conditions guarantee that the equation $x^n = \sum_{i=0}^{n-1} a_ix^i$ has at least one root ...
1
vote
1answer
52 views

How to solve Work->Break->Work pattern questions?

Machine/Person A: Works for 20 hours and take break for 4 hours (repeated cycle) Machine/Person B: Works for 40 hours and take break for 8 hours (repeated cycle) In X amount of hours ( say x is ...
0
votes
2answers
142 views

Math Subject GRE 1268 Problem 64 Flux of Vector Field

What is the value of the flux of the vector field F, defined on $R^3$ by $F(x,y,z) = (x,y,z)$ through the surface $z=\sqrt{1-x^2-y^2}$ oriented with upward-pointing normal vector field? ...
1
vote
4answers
69 views

Find the approximate square root of

Find the approximate square root of $$\dfrac{\left( \dfrac{12}{5}\right)^4 - \left( \dfrac{5}{12}\right)^4 }{\left( \dfrac{12}{5}\right)^2 - \left( \dfrac{5}{12}\right)^2}$$ I tried using the ...
7
votes
5answers
2k views

Math Subject GRE 1268 Question 55

If $a$ and $b$ are positive numbers, what is the value of $\displaystyle \int_0^\infty \frac{e^{ax}-e^{bx}}{(1+e^{ax})(1+e^{bx})}dx$. A: $0$ B: $1$ C: $a-b$ D: $(a-b)\log 2$ E: ...
-1
votes
2answers
39 views

K is the least positive integer divisible by all positive integers less than or equal to 10. Find the total number of factors of K?

the answer is 46. I am not able to figure out how to arrive at that answer
3
votes
2answers
86 views

GRE Math Subject Practice Test Question $53$

f and g are function of a real variable such that $g(x) = \int_0^x f(y)(y-x)dy$ for all $x$. If g is three times continuously differentiable, what is the greatest integer n for which f must be $n$ ...
2
votes
0answers
137 views

GRE Math subject test prep [closed]

What is difficulty level of different test prep resources for the GRE Math subject test? I have come across the following: Princeton Review: Leduc (2010). Cracking the GRE Mathematics Subject Test, ...
4
votes
2answers
147 views

GRE Question ($|x|$ vs $\sqrt{x^2}$)

I just finished taking a Kaplan GRE Practice Test, and I encountered an interesting question with a very vague solution. If you have taken the GRE, then you are probably familiar with the following ...
2
votes
1answer
133 views

Coordinate Geometry and Trigonometry book recommendation for GRE Math Subject Test

I am currently a math major at university and I plan to take GRE Math Subject Test in future (most probably next year). Can you please suggest any good book for revising and brushing up Coordinate ...
2
votes
2answers
61 views

If p and q are prime which elements are in the subgroup? (GRE question)

I was just doing some practice problems in my abstract algebra book trying to get a warm up this morning, but I found a GRE problem in the problem set and I don't know how to solve it. I've tried to ...
0
votes
1answer
50 views

What is the greatest value of b for which and real valued function f that satisfies the following properties must also satisfy f(1)<5

The properties listed are: 1) f is infinitely differentiable on the real numbers 2) f(0) = 1, f'(0) = 1, and f''(0) = 2 3) |f'''(x)| < b for all x in [0,1] This is question 42 from the GRE math ...
1
vote
2answers
63 views

Difference of Square root and order relation

If $a=\sqrt{15} -\sqrt{11}$, $b=\sqrt{27} - \sqrt{23}$, $c=\sqrt{6} - \sqrt{5}$ then which of the following is correct? ...
1
vote
1answer
28 views

Probability x>=yz if the three are randomly distributed in the interval [0,1]

I'm practicing for the GRE subject test and this was one of the questions I missed. I know that the answer is $^{3}/_{4}$, but I'm not quite sure why. One thing I thought of is that the average values ...
2
votes
0answers
87 views

GRE Mathematics Practice Exams

I will be taking the subject test in the near future. Can you recommend me some sources (online or print) from which I can find realistic practice exams? I would like to get my hands on as many ...
0
votes
1answer
83 views

Help me find the flaw in my working?

The problem statements reads as follows Working alone at their respective constant rates, Audrey can complete a certain job in 4 hours, while Ferris can do the same job in 3 hours. Audrey and Ferris ...
0
votes
2answers
39 views

what is the default order and direction of operation?

I have a division like this 16/8/4/2 what is the default way to do calculations when the bracket is not specified . Method 1 : Is it correct to go from right to left like [16/ (8 / { 4 / ...
3
votes
1answer
84 views

Suggestions for calculus review for mGRE

I'm currently studying for the mGRE that will be given in October of this year and I'm having trouble deciding which books to use for the calculus review. I'm currently brushing up in Stewart's ...
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votes
1answer
57 views

Confusion about calculating probability of at least one event occurring

The probability that Tom will win the Booker prize is 0.5, and the probability that John will win the Booker prize is 0.4. There is only one Booker prize to win. What is the probability that at least ...
1
vote
1answer
45 views

How to write this expression about unit digits symbolically?

From a GRE book: "The units digit of a product of positive integers is equal to the units digit of the product of the units digits of those integers." I read this and was thinking... why would you ...
2
votes
1answer
165 views

What is a good combinatorics text for someone studying for the Math GRE Subject Test?

I have NEVER taken a combinatorics course, outside of what one covers in a calculus-based probability course. I would be interested in knowing what would be a suitable combinatorics text for ...
1
vote
0answers
48 views

Issue with a right-angled triangle

The area of the right angle triangle is $18\text{ cm}^2$ and the ratio of its legs is $2:3$. What is the length of the hypotenuse? I assumed the lengths of two sides to be $2x$ and $3x$. I used ...
0
votes
1answer
75 views

What information guarantees a ranking in the 90th percentile is greater than a ranking in the 70th percentile?

Consider the following facts: Person A's salary is in the 90th percentile in Company A. Person B's salary is in the 70th percentile in Company B. The question is: What piece of information is ...
0
votes
2answers
38 views

GRE Quantitative Comparison: Determining range of values satisfying equation involving absolute values

Consider the equation \begin{equation} |2a-1|+|3b+2|=0 \end{equation} Which of the following is true: $a>b$ $a<b$ $a=b$ The relationship cannot be determined. How can one solve for the ...
5
votes
2answers
260 views

GRE basic algebra problem, plugging in works, algebreic method fails me

Simple GRE practice problem, but for some reason my algebraic approach is failing me, can someone point out my error? Given: $$\theta x = x^{-3}(2x)(\frac{x}{2})(2)$$ Question: Which is greater: ...
2
votes
1answer
104 views

Average question GRE

The average daily temperature from 9th to 16th January(both inclusive) was 38.6 C and that from the 10th to 17th January(inclusive) was 39.2 C. what was the temperature on 17th January? I am able ...
0
votes
1answer
62 views

Bit tricky plot on GRE

In a city 90% of the population own a car, 15% own a motor cycle, and everybody owns one or the other or both. Find the percentage of motorcycle owners to car owners. In order to solve it i ...
2
votes
2answers
164 views

Tricky Question from GRE using Ratios

Of two kinds of alloy, silver and copper are contained in the ratio of $5:1$ and the other in $7:2$. What weights of the two alloys should be melted and mixed together so as to makeup a $5$ lb mass ...
1
vote
4answers
83 views

Derivative of $\int_{x}^{0} \frac{\cos xt}{t} dt$

I am working on the following problem: Find the derivative of $f(x)=\displaystyle \int_{x}^{0}\displaystyle\frac{\cos xt}{t}dt$. The answer I am supposed to get is $\displaystyle ...
0
votes
2answers
90 views

Is $\{(x,y)|y=\sin(\frac{1}{x})\}\cup(0,1)$ connected on $R^2$? [duplicate]

Source of definition: http://mathworld.wolfram.com/ConnectedSet.html Definition: A connected set is a set that cannot be partitioned into two nonempty subsets which are open in the relative topology ...
2
votes
1answer
90 views

Number of $0$ in the end of $11^n-1$

$n$ is integer, calculate number of $0$ in the end of $11^n-1$(i.e. largest integer $m$ such that $10^m|11^n-1$). The original question was $n=100$ and I could only choose $m$ from 1 to 5. I ...
1
vote
2answers
55 views

Integrating (floor(x) e^-x) from 0 to inf

How does one obtain the following result: \begin{equation} \int_0^\infty \text{floor}(x) e^{-x} dx= \frac{1}{e-1} \end{equation} where $\text{floor}(x)$ is the greatest integer not exceeding x (from ...
1
vote
1answer
52 views

Equivalent form of a double integral.

I am looking at the second question of this problem set: The iterated integral $\int_0^1 \int_{y/2}^1 e^{x^2} dx \, dy$ can be expressed as (a) $\int_0^1 \int_0^{2x} e^{x^2} dy \, dx$ ...
0
votes
1answer
56 views

Measure of angle formed by chords and two circles

The following is a question from a practice GRE Math Subject Test: In the Euclidean plane, point A is on a circle centered at point O, and O is on a circle centered at A. The circles intersect at ...
0
votes
2answers
46 views

Percentage evaulation Queestion from GRE

A question from GRE book says: A candidate who gets 30 percent marks in an examination fails by 30 marks,but another candidate who gets 42 percent marks get 42 more marks than necessary for ...
1
vote
2answers
84 views

Probability that Three Numbers Drawn Represent Sides of a Triangle

Suppose three numbers are randomly chosen from the following list: \begin{equation} 4,5,7,8,11 \end{equation} What is the probability that the numbers drawn represent sides of a triangle? I posted ...
2
votes
1answer
67 views

Equation of ellipsoid surface obtained by revolving an ellipse

I'm working through the following example from the Princeton Review book: If the ellipse $x^{2} + x^{2/9}=1$ in the $xz-$plane is revolved around the $z-$axis, what's the equation of the resulting ...
2
votes
1answer
68 views

Is it Possible to Add or Multiply Groups?

I came across a GRE Mathematics Subject test question that said the following: "Find the characteristic of the ring $Z_2 + Z_3$." The explanation of the question starts with the statement that ...
1
vote
3answers
168 views

combination problem gre @

On the new years Eve , every member of a community exchanged cards with every other member. if a total of 420 different cards were exchanged , then how many different members were there in the ...
1
vote
2answers
48 views

gre standard deviation probability

I have solved it ,but my answer is wrong above mean mean + n S.d Below mean mean-n s.d S.d' standard deviation and 'n' is number of time s.d
2
votes
2answers
70 views

Number of ways to enter 1,2,3,4,5,6 on the spots marked on three intersecting circles and have the sums of 14

How to solve it , i applied so many method but i could not find right answer, suggest me some method combination question gre 44
0
votes
0answers
115 views

Number of Abelian Groups of Order 36

GRE Subject Test Question: Up to isomorphism, how many abelian groups are there of order 36? The answer given is 4 and the explanation is as follows: Let G be an abelian group with order n. Then G ...
0
votes
0answers
30 views

Convergence of a monotonically increasing sequence

Given $a_n$ monotonically increasing and $a_n>0$. Which of the following converges? (1) $\frac{1}{a_n^2}$ (2) $e^{-a_n}$. I could not see any reason why both (1) and (2) will not converge. If ...
0
votes
3answers
185 views

straight line , gre prolem 170 score hard

what is the distance between the two straight line represented by the equation 3x+4y=10 and 6x+8y=10? A>1 B>2 C>4/3 D>1/2 E>5/2 i try to solve it , firstly find intercept of both line and then ...