Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

In the Math Book, page 26 , there is this problem : x^6 - 3x^3 + 2 = 0, then it states let y = x^3, then it goes to y^2 - 3y^3 + 2 (my first question is here, why is it 3y^3?, is it because y = x^3, so we are doubling?) next, this is factored to (y-2) (y-1) = 0 and the solutions are given as y = 1,2 (I understand this) or x^3 = 1,2 (I understand this) or x = 1, cube root 3 (this is where I am confused as to how there solns are found for x , and especially the cube root 3 i can't see where its coming from). Thank you in advance for the assistance.

\(x^6 - 3x^3 + 2 = 0\) --> \((x^3)^2 - 3x^3 + 2 = 0\). Let \(y=x^3\) --> substitute x^3 with y : \(y^2 - 3y + 2 = 0\) --> \((y-2)(y-1)=0\) --> \(y=2\) or \(y=1\).

If \(y=x^3=2\), then \(x=\sqrt[3]{2}\). If \(y=x^3=1\), then \(x=\sqrt[3]{1}=1\).

Question : At the end of certain sections such as coordinate geometry there are suggested problems from the OG, my question is there an updated version for OG 13? The Math Book I downloaded only goes up to OG 12

Question : At the end of certain sections such as coordinate geometry there are suggested problems from the OG, my question is there an updated version for OG 13? The Math Book I downloaded only goes up to OG 12

There is a set A of 19 integers with mean 4 and standard deviation of 3. Now we form a new set B by adding 2 more elements to the set A. What two elements will decrease the standard deviation the most? A) 9 and 3 B) -3 and 3 C) 6 and 1 D) 4 and 5 E) 5 and 5

There is a set A of 19 integers with mean 4 and standard deviation of 3. Now we form a new set B by adding 2 more elements to the set A. What two elements will decrease the standard deviation the most? A) 9 and 3 B) -3 and 3 C) 6 and 1 D) 4 and 5 E) 5 and 5

The standard deviation of a set shows how much variation there is from the mean, how widespread a given set is. So, a low standard deviation indicates that the data points tend to be very close to the mean, whereas high standard deviation indicates that the data are spread out over a large range of values.

So when we add numbers, which are far from the mean we are stretching the set making SD bigger and when we add numbers which are close to the mean we are shrinking the set making SD smaller.

According to the above adding two numbers which are closest to the mean will shrink the set most, thus decreasing SD by the greatest amount.

Closest to the mean are 4 (equals to the mean) and 5 (1 greater than the mean), thus adding them will shrink the set most, thus decreasing SD most.

Please clarify the statement in GMAT math book: Pg 5 (factors), " If P is a prime number and P is a factor of (ab) then P is a factor of a or P is a factor of b."

It should be "P is a factor of a and/or P is a factor of b."

Please clarify the statement in GMAT math book: Pg 5 (factors), " If P is a prime number and P is a factor of (ab) then P is a factor of a or P is a factor of b."

It should be "P is a factor of a and/or P is a factor of b."

Hi, Valid question. But not necessarily what you say.

For example.

Let the prime number p=2, a=4 and b=3.

ab=12. and P=2 is a factor of ab.

Here p is factor of a not b.

same way if a=3 and b=4. the ab remains same=12. But P is factor of b not a.

In some cases, as you say it can be factor of both a and b. not always.

So it is better to write P is factor of a or P is factor of b.

Please clarify the statement in GMAT math book: Pg 5 (factors), " If P is a prime number and P is a factor of (ab) then P is a factor of a or P is a factor of b."

It should be "P is a factor of a and/or P is a factor of b."

Hi, Valid question. But not necessarily what you say.

For example.

Let the prime number p=2, a=4 and b=3.

ab=12. and P=2 is a factor of ab.

Here p is factor of a not b.

same way if a=3 and b=4. the ab remains same=12. But P is factor of b not a.

In some cases, as you say it can be factor of both a and b. not always.

So it is better to write P is factor of a or P is factor of b.

Hope it helps.

Thanks, you example helps the understanding. However, I feel that by writing "or" , you exclude the option that P may be a factor of both. So, I think mentioning "and/or" would be more clear, at least for me.

None the less. I have understood the concept. Thanks

thanks for the tips. i need to GMAT MATH BOOK.I will get my hands on one of the paper tests, the Barron’s practice tests I had were on the computer only and I did not have the corresponding book with the scale. I did a Veritas test and got a 520 (doing better in the verbal section). Is it reasonable to think I could get 600 or more on the GMAT with good preparation? Thanks

Hi Bunuel/Karishma, In the GMAT Math Book (page #5), it says

• If \(a\) is a factor of \(b\) and \(b\) is a factor of \(a\), then \(a=b\) or \(a=-b\).

I can get it but it creates confusion when Veritas Arithmetic book (page # 20) says "Negative numbers are never factors.". So,where is the catch ?

P.S: I hope it's the right place to ask these questions. As I don't post much questions on Math forum so if this is not the right place please move it to the right forum.Thank you!
_________________

Hi Bunuel/Karishma, In the GMAT Math Book (page #5), it says

• If \(a\) is a factor of \(b\) and \(b\) is a factor of \(a\), then \(a=b\) or \(a=-b\).

I can get it but it creates confusion when Veritas Arithmetic book (page # 20) says "Negative numbers are never factors.". So,where is the catch ?

P.S: I hope it's the right place to ask these questions. As I don't post much questions on Math forum so if this is not the right place please move it to the right forum.Thank you!

Yes, for the GMAT we consider only positive factors.
_________________

~~To acknowledge my assistance in your learning through this post, please reward by giving KUDOS~~ ~~ When the going gets tough , the tough gets going-- I will score 700 . ~~

gmatclubot

Re: GMAT Math Book
[#permalink]
21 Nov 2014, 08:11

Happy New Year everyone! Before I get started on this post, and well, restarted on this blog in general, I wanted to mention something. For the past several months...

It’s quickly approaching two years since I last wrote anything on this blog. A lot has happened since then. When I last posted, I had just gotten back from...

Post-MBA I became very intrigued by how senior leaders navigated their career progression. It was also at this time that I realized I learned nothing about this during my...