GMAT Math Book : GMAT Quantitative Section - Page 7
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# GMAT Math Book

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19 Jun 2014, 08:19
sagnik242 wrote:
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 $$x=\sqrt[3]{1}=1$$.

Hope it's clear.
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28 Jun 2014, 19:12
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

Thanks
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29 Jun 2014, 03:38
sagnik242 wrote:
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

Thanks

Check here: og-q-types-analysis-92380.html

You might also find the following posts helpful.

OG:
the-official-guide-quantitative-question-directory-143450.html
quantitative-review-2nd-edition-directory-164896.html
gmat-club-guide-to-the-gmat-official-guide-11-12-13th-ed-85956.html

ALL YOU NEED FOR QUANT: all-you-need-for-quant-140445.html
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29 Jun 2014, 09:06
Thanks

Question -> page 105 of the PDF of the Math Book

example #4 for standard deviation, is the answer D or E, because they both contain 5
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29 Jun 2014, 09:10
sagnik2422 wrote:
Thanks

Question -> page 105 of the PDF of the Math Book

example #4 for standard deviation, is the answer D or E, because they both contain 5

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29 Jun 2014, 16:48
Sorry, lazy on my part :

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
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30 Jun 2014, 02:13
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Expert's post
sagnik2422 wrote:
Sorry, lazy on my part :

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.

Similar questions to practice:
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Hope it helps.
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15 Jul 2014, 21:30
this is an amazing source
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18 Jul 2014, 10:51
A minor comment for the next revision - The Triangles topic is missing from the Table of Contents.
Thanks!
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18 Jul 2014, 11:09
Dienekes wrote:
A minor comment for the next revision - The Triangles topic is missing from the Table of Contents.
Thanks!

Isn't it in the original post?
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21 Jul 2014, 09:39
Bunuel wrote:
Dienekes wrote:
A minor comment for the next revision - The Triangles topic is missing from the Table of Contents.
Thanks!

Isn't it in the original post?

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21 Jul 2014, 10:31
Dienekes wrote:
Bunuel wrote:
Dienekes wrote:
A minor comment for the next revision - The Triangles topic is missing from the Table of Contents.
Thanks!

Isn't it in the original post?

Thanks. Will update it.
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03 Aug 2014, 03:40
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."
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03 Aug 2014, 03:57
akhilbajaj wrote:
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.
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03 Aug 2014, 04:02
Gnpth wrote:
akhilbajaj wrote:
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
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02 Sep 2014, 23:39
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
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12 Sep 2014, 22:11
Was wondering on how to prepare for the Math section... Very relieved to come across this post.. Great effort guys "kudos"
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29 Oct 2014, 06:37
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!
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21 Nov 2014, 04:06
bagdbmba wrote:
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.
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21 Nov 2014, 08:11
walker wrote:
GMAT MATH BOOK
Open GMAT Club project

Authors: bb, walker, Bunuel, shrouded1

--------------------------------------------------------

6 topics of the book are included in GMAT ToolKit App (iPhone/iPod Touch)

--------------------------------------------------------

- GMAT math diagnostic test

- Number theory
- Percents
- Absolute value
- Algebra
- Triangles
- Polygons
- Circles
- Coordinate geometry
- Standard Deviation
- Probability
- Combinatorics
- Sequences and Progressions
- 3-D Geometries

A downloadable PDF of the GMAT Club's Math Book is available here

Resources:

materials that are not currently included in the Math Book.

- Graphic approach to problems with inequalities - walker
- Everything about Factorials on the GMAT - Bunuel
- Compilation of tips and tricks to deal with remainders. - sriharimurthy
- Word Problems Made Easy - sriharimurthy
- 'Work' Word Problems Made Easy - sriharimurthy
- 'Distance/Speed/Time' Word Problems Made Easy - sriharimurthy
- Guide to series and sequences... arithmetic and geometric - benjiboo
- How to draw Venn diagrams - new!- whiplash2411

- Official Guide for GMAT® Review, 13th Edition Quantitative Question Directory

[Reveal] Spoiler: Images
Attachment:

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

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