TestMagic Forums - GMAT Math

A new GMAT exam Prep website! (GMATquestion.com)

GMATquestion — Fri, 20 Nov 2009 18:00:30 GMT

Hello everyone,

I am new to this forum, but already midway through studying for the GMAT exam.

My friends and I decided to create a website to help us, and others like us study for the GMAT exam.

We finished developing the website very recently, and i was wondering what you think of it.

I would really appreciate any comments, constructive criticism, etc.

The website is GMATquestion.com

Thanks! :)

PS: sequence need help

srinivas124 — Wed, 18 Nov 2009 12:25:15 GMT

for every integer K from 1 to 10 , inclusive, the Kth term of the sequence is given by ((-1)^(K+1))(1/2^K). If T is the sum of first 10 terms in the sequence, then T is:
1. greater than 2
2. between 1 & 2
3. between 1/2 & 1
4. between 1/4 & 1/2
5. less than 1/4

answer:4:rolleyes:

problems

mw13 — Mon, 16 Nov 2009 19:05:33 GMT

1) Are x and y both positive?
Statement (1) 2x - 2y = 1
Statement (2) x/y > 1

OA

SPOILER: C

2) For which of the following functions f is f(x) = f(1-x) for all of x?
A) f(x) = 1-x
B) f(x) = 1-x^2
C) f(x) = x^2 - (1-x)^2
D) f(x) = x^2(1-x)^2
E) f(x) = x/1-x

OA

SPOILER: D

3) What is the hundreths digit of the decimal z?
Statement (1) The tenths digit of 100z is 2.
Statement (2) The units digit of 1000z is 2.

OA

SPOILER: E

4) If m > 0 and n > 0, is m+x/n+x > 0?
Statement (1) m < n
Statement (2) x > 0

OA

SPOILER: C

5) Is z equal to the median of the three positive integers x,y, and z?
Statement (1) x < y + z
Statement (2) y = z

OA

SPOILER: B

6) If n is a positive integer, is n^3 - n divisible by 4?
Statement (1) n = 2k + 1 where k is an integer
Statement (2) n^2 + n is divisible by 6

OA

SPOILER: A

Percentage Problem

adi14sks — Thu, 12 Nov 2009 02:24:47 GMT

I am a bit confused in this problem. The confusion lies with the assumption.
Please help me with this!!

The total cost of producing item X is equal to the sum of item X�s fixed cost and variable cost. If the variable cost
of producing X decreased by 5% in January, by what percent did the total cost of producing item X change in
January?
(1) The fixed cost of producing item X increased by 13% in January.
(2) Before the changes in January, the fixed cost of producing item X was 5 times the variable cost of producing
item X

In this, if i look at the 1st then this is not sufficient . But for the 2nd if i need ot solve i will have to assume that fixed cost remains constant.then only i can solve it . So is this a valid assumption or shud i go with c wherein i know that fixed cost increases by 13%.

can't figure these out...

ss1 — Wed, 11 Nov 2009 21:57:31 GMT

for every integer k from 1 to 10 inclusive, the kth term of a certain sequence is given by [(-1)^(k+1)](0.5^k). if T is the sum of the first 10 terms in the sequence, then T is:
a)greater than 2
b) between 1 and 2
c)between 1/2 and 1
d)between 1/4 and 1/2
e)less than 1/4

SPOILER: OA: D

can't figure this out for the life of me! tried putting k as one, to get the first value of the sequence, got it as 0.5, and then to get the last term, put k as 10 to get (-0.5^10). used a+l*n/2, and got a weird answer. no idea where to go from here:(

Al,Pablo and Marsha shared the drving on a 1500 mile trip. which one of the three drove the greatest distance?
1)al drove one hour longer than Pablo but at an average speed of 5mph slower than Pablo.
2)Marsha drove 9 hours and averaged 50mph

SPOILER: OA: E. my answer:C

whena certain tree was first planted, ti was 4 feet tall, and the height of the tree increased by a certain factor for the next 6 years. at the end of the 6th year, the tree was 1/5 taller than at the end of the 4th year. by how many feet did the height of the tree increase each year?
a)3/10
b)2/5
c)1/2
d)2/3
e)6/5

SPOILER: OA: D

the sequence a₁, a_2,, a₃...a_n of n integers is such that a_k= k if k is odd, and a_k=-a_k-1 if k is even. is the sum of the terms in the sequence positive?
1)n is odd
2)a_n is postive

SPOILER: OA: D

a manufacturer conducts a survey to find out how many people buy products p and Q. what fraction of the people said they buy neither product P nor Q?
1) 1/3 of the people said they buy P but not Q
2)1/2 of the people surveyed said they buy product Q

SPOILER: OA: C

my question, putting them both together we have P+Q- P intersection Q+ neither = total. here we don't have just Q, we dont have the intersection of P and Q, then shouldnt the answer be E?

Some one... please help

OneDayI'll — Wed, 11 Nov 2009 14:41:30 GMT

Can some one please help me with this.
I always get confused with these ones.

Please tell me a good way to solve this

Three of the four vertices of a rectangle in the

xy-coordinate plane are (-3, 10), (2, 10),

and (2, 1). What is the fourth vertex?

Guidance needed..

OneDayI'll — Tue, 10 Nov 2009 01:03:48 GMT

x and y are positive, is x3 > y?
(1) sqr(x) > y

(2) x > y

As per me the solution is D. but OA - E

cant solve these!

ss1 — Mon, 09 Nov 2009 11:50:31 GMT

hey guys, i just cant crack these, any help would be appreciated:
For every positive even integer n, the function h(n) is defined to eb the product of all the even integers from 2 to n, inclusive. If p is the smallest prime factor of h(100)+1, then p is:
A) Between 2 and 10
B) Between 10 and 20
C) Between 20 and 30
D) Between 30 and 40
E) Greater than 40

SPOILER: OA: E

A committee of 3 people is to be chosen from 4 married couples. what is the number of different committess that can be chosen if two people who are married to each other cannot both serve on the committee?
A) 16
b)24
C)26
D)30
E)32

SPOILER: answer: E

Perimeter of isosceles right triangle is 16 +16√2, what is hypotenuse?
a. 8
b. 16
c. 4√2
d. 8√2
e. 16√2

SPOILER: OA: b

My answer: 2x+y= 16+16(2^0.5)
Also, 2(x^2)=y^2, so y= x(2^0.5)
And we have 16+16(2^0.5)= 2x + x(2^0.5), but I get two values for x, 8 and 16. How to solve this?

Also, if we have one point in the 2nd quadrant (x=-(3^0.5), y=1), then if we have to find the point in the first quadrant that is the other point of a 90 degree triangle, do we invert the values? or just the sign (the negative of x to a positive). this is actually a question, but i cant paste the drawing here

how to solve such questions

ss1 — Sun, 08 Nov 2009 09:58:28 GMT

Jane's credit card account, the average balance for a 30-day billing cycle is the (arithmetic mean) of the daily balances at the end of each of the 30 days. At the end of a certain 30 day billing cycle, Jane�s card account had a balance of $600. Jane made a payment of $300 on the account during the billing cycle. If no other amounts were added
or subtracted from the account during the billing cycle, what was the average daily balance on Jane�s account for the billing cycle?
A) Jane�s payment was credited on the 21st day of the billing cycle
B) The average daily balance through 25th day of the billing cycle was $540.

OA:D

Beginning in January of last year, Carl made deposits of $120 into his account on the 15th of each month for several consecutive months and then made withdrawals of $50 from the account on the 15th of each of the remaining months of last year. There were no other transactions in the account last year. If the closing balance of Carl�s account for May of last year was $2,600, what was the range of the monthly closing balances of Carl�s account last year?
(1) Last year the closing balance of Carl�s account for April was less than $2,625.
(2) Last year the closing balance of Carl�s account for June was less than $2,675.

OA:C

I can never understand how to solve such questions, can anyone please help? I don�t even know how to approach them. Thank you.

Remainder Problem!!

adi14sks — Sun, 08 Nov 2009 03:46:35 GMT

When the integer x is divided by the integer y, the remainder is 60. Which of the following is a possible value of
the quotient x/y?
I. 15.15 II. 18.16 III. 17.17
(A) I only (B) II only (C) III only (D) I and II only (E) I and III only

GMATprep - Practice Test 1 => Have some problems figuring out right answers...

GMAT n00b — Sat, 07 Nov 2009 00:43:06 GMT

Dear GMAT professionals, ;)
I did the first free and available for a quick and easy download (no registration required).", "style=\"display: block;padding: 5px;z-index: 100;background-color: #323232;color: #fff;filter:alpha(opacity=90); /* for IE */opacity:0.9; /* CSS3 standard */width:auto;-moz-border-radius: 5px; /* this works only in camino/firefox */-webkit-border-radius: 5px; /* this is just for Safari */\"");' onmouseout='GAL_hidepopup();' style="text-decoration: none; border-bottom-style:dashed; border-bottom-width: 1px"> GMATprep Practice test and scored 650. When reviewing my mistakes, I still couldn't figure out the answers to all of the questions. I hope that you can help me and I hope that my questions aren't too stupid! :)

#1
If 5^21 * 4^11 = 2 * 10^n what is the value of n?
The answer is 21.

What I tried to do:
5^21 * 4^11 = 5^11 * 5^10 * 4^11 = 20^11 * 5^10. But then I got stuck...

#7
In isoceles RST what is the measure of (1) The measure of (2) The measure of The answer is Statement 1 alone is sufficient but 2 is not.

Is this the answer because we don't know which of the two angles are the same? Statement 1

states that T is 100 that means that R and S are the same and therefore 40 each? Statement

2 states that S is 40 but we do not know whether one of the two other angles is also 40?

#17
Is the integer k divisible by 4?
(1) 8k is divisible by 16
(2) 9k is divisible by 12
Answer is Statement 2 alone is sufficient.

I plugged in several integers for k and found out that 8k is divisble by 16 for k=2 but in this case, k is not divisible by 4. None of the numbers I found for 9k/12 worked also for k/4 (e.g.3,8,...). Is there a more efficient way to solve this question than just plugging in numbers?

#18
If the operation [+-*/] (it is a strange symbol in the actual test) is defined for all

integers a and b by a [+-*/] b = a+b-ab, which of the following must be true for all integers a b c?
1) a[+-*/]b = b[+-*/]a
2) a[+-*/]0 = a
3) (a[+-*/]b)[+-*/]c = a[+-*/](b[+-*/]c)
Answer is all are true.

I really don't know how to solve this problem.

#24
To furnish a room in a model home, an interior decorator is to select 2 chairs and 2 tables from a collection of chairs and tables in a warehouse that are all different from each other. If there are 5 chairs in the warehouse and if 150 different combinations are possible, how many tables are an in the warehouse?
Answer is 6.

#28
If m, r, x, and y are positive, is the ratio of m/r = x/y?
(1) m/y = x/r
(2) (m+x)/(r+y)=x/y
Answer: Statement 2 is alone sufficient but statement 1 isn't.

#33
If p is a positive integer, what is the value of p?
(1) p/4 is a prime number
(2) p is divisible by 3
Answer: Both together are sufficient.

I found 12, but how can I be sure that 12 is the only existing integer that fulfills the two statements?

I would be really grateful if you could help me with my problems....

Thanks a lot!!! :)

odds in favor of?

ss1 — Thu, 05 Nov 2009 20:27:37 GMT

are questions of probability asking odds in favor of or odds against included in the gmat course?

some hard OGs

ss1 — Wed, 04 Nov 2009 12:55:15 GMT

1)X^4 + y^4=100, then the greatest possible value of x is between:
a)0 and 3 B) 3 and 6 c) 6 and 9 d) 9 and 12 e)12 and 15
OA: B

2)In the xy plane, what is the y-intercept of line l?
1) The slope of line l is 3 times its y intercept
2) The x-intercept of line l is -1/3
M=3c, so the equation would be: y=mx+c, so y=3c.x +c
2)when y=0, x=-1/3. So here we have: 0=3c(-1/3)+c. which comes to:-c+c=0. What am I doing wrong here? Shouldn�t the answer be C?OA:E
Also, does the xy plane mean quadrant 1?

3) six machines, each working at the same constant rate, together can complete a certain job in 12 days. how many additional machines, each working at the same constant rate will be needed to finish the job in 8 days?
a)2 b)3 c)4 d)6 e)8
OA: B

4)a certain city with a population of 132,000 is to be divided into 11 voting districts. and no district is to have a population that is 10% greater than the population of any other district. what is the minimum possible population that the least populated district could have?
a)10,700 b)10,800 c)10,900 d)11,000 e)11,100
OA: D

OG 12 Q213

ss1 — Thu, 29 Oct 2009 21:40:53 GMT

In an electric circuit, two resistors with resistances x
and y are connected in parallel. In this case, if r is the
combined resistance of these two resistors, then the
reciprocal of r is equal to the sum of the reciprocals of
x and y. What is r in terms of x and y ?
(A) xy
(B) x + y
(C)1/(x + y)
(D)(Xy)/(x + y)
(E)(x + y)/(xy)

Cant the answer be x+y=r? OA: D

official practice test questions

ss1 — Mon, 26 Oct 2009 17:44:56 GMT

At a certain company, the average number of experience (in years) for males is 9.8, and 9.1 for female employees. What is the ratio of the number of male employees to female employees?
1)there are 52 males at the company
2)the average number of experience for the company’s male and female employees combined is 9.3 years

answer: B

The rate of a reaction is directly proportional to the square of the concentration of A and inversely proportional to concentration of B. If B increases by 100%, which of the following is closest to the % change in concentration of A required to keep the rate unchanged?
a. 100% decrease
b. 50% decrease
c. 40% decrease
d. 40% increase
e. 50% increase

answer: d

A list of measurements in increasing order is 4, 5, 6, 8, 10, and x. If median of the measurements is 6/7 times the mean, what is the value of x?
a. 16
b. 10
c. 12
d. 13
e. 15
answer:a

If x and y are integers greater than 1, is x a multiple of y?
a. 3(y^2) + 7y = x
b. x^2 – x is a multiple of y

a manufacturer conducted a survey to find out how many people buy product P and Q. what fraction of the people surveyed said they bought neither P nor product Q?

1) 1/3 of the people surveyed said they bought product P but not Q
2) � said they bought product Q

answer :c