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GMAT Math Book [#permalink]
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GMAT MATH BOOKOpen GMAT Club projectAuthors: bb, walker, Bunuel, shrouded1 Get The Official GMAT Club's App  GMAT TOOLKIT 2. The only app you need to get 700+ score! [ iOS App] [ Android App]  Table of contents: GMAT math diagnostic test Number theory Percents Absolute value Algebra  Triangles Polygons Circles Coordinate geometry Standard Deviation Probability Combinatorics Sequences and Progressions 3D GeometriesA downloadable PDF of the GMAT Club's Math Book is available hereResources:materials that are not currently included in the Math Book. Statistics Made Easy  All in One Topic!  Bunuel Collection of mathrelated links  timetrader 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 Get The Official GMAT Club's App  GMAT TOOLKIT 2. The only app you need to get 700+ score! [ iOS App] [ Android App]  Attachment:
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Originally posted by walker on 29 Nov 2009, 14:56.
Last edited by walker on 25 Jan 2015, 09:14, edited 43 times in total.



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Re: GMAT Math Book [#permalink]
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RULES FOR AUTHORSColors  black/white/gray + green (#459926). Please, do not use any other color highlighting. Images Maximum size: 290px*290px. Format: PNG. Transparent background.  No long formulas. They are images in a final document and have to be not wider than 290px. AttachmentsEmbed Attachments (Images) using imgtag with url Code: [img]http://gmatclub.com/forum/download/file.php?id=10096[/img] Attachments at the end of posts have to be hidden using spoilertag: Code: [spoiler=Images]................[/spoiler] Structure and content Keep structure as simple as possible. Don't forget that the book will be also used for a mobile application.  Avoid long blocks.  Avoid redundancy in headers, text and structure.  Use more "formal" language.  Go from simple definitions to the hardest concepts.  Weight of any concept in your post should be as close as possible to frequency of using this concept in GMAT.  Use only own examples, don't copypast problems.  Don't forget about "Resources" list at the end of your post.  Test your post in a simple way: Choose a random problem from your topic. Does your post help to solve this problem? How easy anyone can find related to the problem information? Code: [size=150][color=#459926][b]TITLE[/b][/color][/size]
.... {header information: author, editors and so on}
[size=150][color=#459926][b]Header 1[/b][/color][/size]
text + images
[size=150][color=#459926][b]Header 2[/b][/color][/size]
text + images
[b]Example #1[/b] [b]Q[/b]:text [b]Solution:[/b] text
[b]Example #2[/b] [b]Q[/b]:text [b]Solution:[/b] text
.....
[size=150][color=#459926][b]Resources[/b][/color][/size]
all useful links New topicsIf you are going to create a new topic, please, include following information into Book's table of contents to avoid creating the same topic at the same time by different authors: Code:  [color=#999999][b]Standard Deviation[/b][/color]  [color=#999999][i]walker: next topic[/i][/color] The name of a new topic should begin with " Math: " and be as short as possible.
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Re: GMAT Math Book [#permalink]
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Hello everybody, This is my first post. I converted everything I could find in the GMAT math project and more into an ADOBE file to make it look sharper. All the information that you guys post is wonderful stuff and I just wanted to share these files I converted with everyone. I can do more later if anyone wishes. Marcel



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Second Post of converted files Marcel



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Seventh Post of Converted files



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Last Post of GMAT Open Math Project As a note I also converted the Verbal tips posted by the members and practice problems including the 3000 reading comp passages if any one would like those as well. All the best, Marcel



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Re: GMAT Math Book [#permalink]
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30 Apr 2010, 12:25
Hi there, Can anybody help with this: how many 3 digit no. are possible using the digit 0, 1, 4, 5, 7 & 9?
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Re: GMAT Math Book [#permalink]
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30 Apr 2010, 14:57
sheetalsanjana wrote: :D Hi there, Can anybody help with this: how many 3 digit no. are possible using the digit 0, 1, 4, 5, 7 & 9? If repetition is allowed, then: 5(any digit out of 6, but 0)*6(any digit out of 6)*6(any digit out of 6)=180, we can not have 0 as the first digit, as in this case number won't any longer be 3digit and becomes 2digit. If repetition is not allowed, then: 5(any digit out of 6, but 0)*5(any digit out of 6first digit=5)*4(any digit out of 6first&second digits=4)=100.
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Re: GMAT Math Book [#permalink]
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20 Feb 2013, 02:38
Hello to all,
My first post on this forum.
I have a question about the formulas to add an element to a set on p103. Are they also valid for sets which contain a limited amount of numbers, for example a set consisting of four or five numbers? If you use the number two formula, and you add a number to a small set, the mean will change significantly. I think this formula is only valid for large sets in which the mean is more or less invariable when adding numbers?
I just tried it with a small set of numbers, and the formula didn't work.



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Re: GMAT Math Book [#permalink]
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20 Feb 2013, 10:11
jorisboris, I am not sure if I understand you, but so far I think you are misunderstanding the formulas (are you referring to the formulas labeled as 1), 2), 3) and 4) in p103?) Translated to words: 1) If the number you add to the set (y) is higher than the standard deviation (in formulas: if the distance from y to the median is higher than the distance of the standard deviation to the median, if y > STD) then the standard deviation of the set will increase (in formulas: the new standard deviation will be higher than the old standard deviation). Or what is the same: new numbers added to the set will reduce the STD if they present less deviation than the STD (they are closer to the mean than the STD range), will increase the STD if they are further away from the mean than the range of the STD, will keep the STD the same if they are exactly as far away from the mean as the STD and will minimize as much as possible the STD if they are exactly equal to the mean (they add a deviation of 0, so the STD has the same total deviation, +0 is added) but more term to divide, thus decreases as much possible). Of course if you have 5 terms and you add a 6th term to the set that is exactly the same as the mean the STD will decrease much more than if you have 1000 terms with a huge STD and you just add one new element to the set. Still, the behavior will be the same, as these considerations are QUALITATIVE, not QUANTITATIVE. Check my notes attached. In summary, these formulas only explain the behavior of the Standard Deviation based on the kind of number that you add to the set. Colors match, so line 1) refers to red point, line 2) refers to orange point, etc. Does this solve your question?
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Re: GMAT Math Book [#permalink]
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19 Jun 2014, 09:06
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 (y2) (y1) = 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.



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Re: GMAT Math Book [#permalink]
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19 Jun 2014, 09:19
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 (y2) (y1) = 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 : \(y^2  3y + 2 = 0\) > \((y2)(y1)=0\) > \(y=2\) 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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Re: GMAT Math Book [#permalink]
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29 Jun 2014, 17:48
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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Re: GMAT Math Book [#permalink]
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30 Jun 2014, 03:13
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. Answer: D. Similar questions to practice: acertainlisthasanaverageof6andastandarddeviation97473.htmlacertainlistof200testscoreshasanaverage131448.htmlacertainlistof100datahasanaveragearithmeticmean87743.htmlsetxconsistsof100numberstheaveragearithmeticmean103536.htmlsetaconsistsoffivedifferentnumberssetbconsistsof155868.htmlnewdsset15065360.htmlm0372087.htmlateamofresearchersmeasuredeachoftensubjectsreactio123873.htmlHope it helps.
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Collection of Questions: PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.
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Re: GMAT Math Book [#permalink]
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29 Oct 2014, 07:37
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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