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# GMAT Flashcards

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Intern
Joined: 25 Jun 2011
Posts: 47

Kudos [?]: 1 [0], given: 7

Location: Sydney

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24 Mar 2012, 00:44
Hi,

I've got another question; these flashcards are really good btw :)

On page 33, in the Standard Deviation 3 slide, there is a question of "What is the fastest way to estimate standard
deviation (without calculating it)?" I really want to know the answer, but I don't see the answer in the answer slide?

Am I missing something?

Many thanks.
Diana

Kudos [?]: 1 [0], given: 7

Intern
Joined: 25 Jun 2011
Posts: 47

Kudos [?]: 1 [0], given: 7

Location: Sydney

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24 Mar 2012, 01:15
Sorry, another question.

On page 44, in the Triangle 8 (Ultra Hard) question explanation,

Slide says "In the extreme case when Angle ABC is right, the triangle BOC is isosceles and thus a^2 =1/a and the area of the triangle ABC is a = 1."

I don't get how you can tell that the height of the triangle (a^2) is equal to half of the base (1/a) when the triangle is isosceles?

Thanks a lot

Kudos [?]: 1 [0], given: 7

Founder
Joined: 04 Dec 2002
Posts: 15858

Kudos [?]: 29064 [0], given: 5259

Location: United States (WA)
GMAT 1: 750 Q49 V42

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24 Mar 2012, 14:09
dianamao wrote:
bb wrote:
dianamao wrote:
I'm a bit confused on the Average 2 question on page 29.

It says that "The average of 10 consecutive integers is 12." Since this is an evenly spaced set, the median is also 12. But this is a set that contains an even number of integers, so how can the median be an integer?

E.g. the median for {2,3,4,5} is 3.5 (non-int)
the median for {5,6,7,8} is 6.5 (non-int)

This question? Where does the median come into play?
Am i missing something?

The median doesn't come into play, but I just had a general question about the median of a set of numbers (that arose when I was looking through this particular Average question).

I thought the median of a set of even number of elements should be a non-int? But in this question, the mean is 12, and since it's an evenly spaced set, the median is 12 also. I just don't understand how the median can be 12?

Thanks

You are right. 12 cannot be the average of the set of 10 consecutive integers. I will change it to be 9 numbers instead. Thank you.
_________________

Founder of GMAT Club

Just starting out with GMAT? Start here... or use our Daily Study Plan

Co-author of the GMAT Club tests

Kudos [?]: 29064 [0], given: 5259

Founder
Joined: 04 Dec 2002
Posts: 15858

Kudos [?]: 29064 [0], given: 5259

Location: United States (WA)
GMAT 1: 750 Q49 V42

### Show Tags

24 Mar 2012, 14:21
dianamao wrote:
Hi,

I've got another question; these flashcards are really good btw :)

On page 33, in the Standard Deviation 3 slide, there is a question of "What is the fastest way to estimate standard
deviation (without calculating it)?" I really want to know the answer, but I don't see the answer in the answer slide?

Am I missing something?

Many thanks.
Diana

(officially, on the GMAT, you usually never have to CALCULATE the SD but you must know how to calculate it, which really means is that you will have to calculate it at least for a few numbers)

This is the answer (taking the above into consideration)
We don't need to calculate as decrease in all elements of a set by a constant percentage will decrease the standard deviation of the set by the same percentage (the average is decreased by 17% as well as the difference between average (mean) and all elements or their squares. Thus the decrease in standard deviation is 17%.
_________________

Founder of GMAT Club

Just starting out with GMAT? Start here... or use our Daily Study Plan

Co-author of the GMAT Club tests

Kudos [?]: 29064 [0], given: 5259

Founder
Joined: 04 Dec 2002
Posts: 15858

Kudos [?]: 29064 [0], given: 5259

Location: United States (WA)
GMAT 1: 750 Q49 V42

### Show Tags

24 Mar 2012, 14:25
dianamao wrote:
Sorry, another question.

On page 44, in the Triangle 8 (Ultra Hard) question explanation,

Slide says "In the extreme case when Angle ABC is right, the triangle BOC is isosceles and thus a^2 =1/a and the area of the triangle ABC is a = 1."

I don't get how you can tell that the height of the triangle (a^2) is equal to half of the base (1/a) when the triangle is isosceles?

Thanks a lot

There is a shortcut that says if there is a triangle with angles 90, 60, and 30, then the side (hypotenuse) equals to 2x the side opposite of the 30 degree angle.
Here is more about it: ds-triangle-m09q07-72173.html?kudos=1
_________________

Founder of GMAT Club

Just starting out with GMAT? Start here... or use our Daily Study Plan

Co-author of the GMAT Club tests

Kudos [?]: 29064 [0], given: 5259

Intern
Joined: 12 Oct 2008
Posts: 13

Kudos [?]: 4 [0], given: 2

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27 Mar 2012, 09:20
I think there is a type on page 43 slide 10, height of equilateral tringale is given as a3/2 . I Guess height should be less than side of equilateral triangle.

Kudos [?]: 4 [0], given: 2

Founder
Joined: 04 Dec 2002
Posts: 15858

Kudos [?]: 29064 [0], given: 5259

Location: United States (WA)
GMAT 1: 750 Q49 V42

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27 Mar 2012, 11:12
AmarSharma wrote:
Page 51 and 52 are repeats, CG slide 8,9,10 from page 49 and 50.

Thank you. I see that - I am updating those pages.
_________________

Founder of GMAT Club

Just starting out with GMAT? Start here... or use our Daily Study Plan

Co-author of the GMAT Club tests

Kudos [?]: 29064 [0], given: 5259

Founder
Joined: 04 Dec 2002
Posts: 15858

Kudos [?]: 29064 [0], given: 5259

Location: United States (WA)
GMAT 1: 750 Q49 V42

### Show Tags

27 Mar 2012, 11:22
AmarSharma wrote:
I think there is a type on page 43 slide 10, height of equilateral tringale is given as a3/2 . I Guess height should be less than side of equilateral triangle.

Thank you #2 - it should be $$a\frac{\sqrt {3}}{2}$$

The square root sign got lost somewhere.... Thank you.
_________________

Founder of GMAT Club

Just starting out with GMAT? Start here... or use our Daily Study Plan

Co-author of the GMAT Club tests

Kudos [?]: 29064 [0], given: 5259

Founder
Joined: 04 Dec 2002
Posts: 15858

Kudos [?]: 29064 [0], given: 5259

Location: United States (WA)
GMAT 1: 750 Q49 V42

### Show Tags

27 Mar 2012, 11:27
Thanks. I have updated the slides and updated the PDF file.
_________________

Founder of GMAT Club

Just starting out with GMAT? Start here... or use our Daily Study Plan

Co-author of the GMAT Club tests

Kudos [?]: 29064 [0], given: 5259

Intern
Joined: 25 Jun 2011
Posts: 47

Kudos [?]: 1 [0], given: 7

Location: Sydney

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28 Mar 2012, 17:40
I'm confused on the Volume/Mixture Problems (Hard) question on page 38.

Could someone pls explain what is the purpose of (x‐15)(y+4)=(x+20)(y‐3)?

I understand that it is # of chickens x # of days of feed left, but what does this mean?

Thanks a lot,
Diana

Kudos [?]: 1 [0], given: 7

Intern
Joined: 01 Apr 2012
Posts: 7

Kudos [?]: [0], given: 0

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05 Apr 2012, 07:47
Wow I found this to be very useful if you tackle this before taking on the OG you'll be surprised on your results!!

Kudos [?]: [0], given: 0

Manager
Joined: 06 Jul 2011
Posts: 213

Kudos [?]: 71 [0], given: 39

Location: Accra, Ghana

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09 Apr 2012, 02:48
I now have some resources that I can constantly look over daily to remember the stuff I should be learning.

Kudos [?]: 71 [0], given: 39

Founder
Joined: 04 Dec 2002
Posts: 15858

Kudos [?]: 29064 [0], given: 5259

Location: United States (WA)
GMAT 1: 750 Q49 V42

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10 Apr 2012, 12:34
catty2004 wrote:
The office of 120 is split between male and female
employees at the ratio of 3:5. If 40% of the
employees are married and 20 of the married
employees in the office are men, how many of the
women working in the office are single?

In your matrix you drew, where are you getting 45 and 75? It just seems like you are pulling them out of thin air.

Note: Above question was posted by RyanP, though I have the same question.

the ratio is 3:5, so that means if you divide 120 by (3+5), you will get 15.
Now multiply 3 by 15 and 5 by 15 and you get those numbers (yes, out of thin air though with the help of some math)

Can someone please explain the reason why you can do 120 / by (3+5)? Also any alternative solution to this type of question without drawing a matrix? Thanks!

We know that there is a ratio of 3:5.
We must understand how ratios work to be able to solve the problem.

The minimum number of people in the office is 8 - do you agree? (If not, this is the question to address)
The next possible number is 16, 24, 32, etc ..... 120.

Does this help?
P.S. the matrix/table is the easiest way to solve this question. It is quite a math exercise to solve it with equations.
_________________

Founder of GMAT Club

Just starting out with GMAT? Start here... or use our Daily Study Plan

Co-author of the GMAT Club tests

Kudos [?]: 29064 [0], given: 5259

Intern
Joined: 03 Jun 2011
Posts: 3

Kudos [?]: [0], given: 7

Location: India

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11 Apr 2012, 20:13
catty2004 wrote:
The office of 120 is split between male and female
employees at the ratio of 3:5. If 40% of the
employees are married and 20 of the married
employees in the office are men, how many of the
women working in the office are single?

In your matrix you drew, where are you getting 45 and 75? It just seems like you are pulling them out of thin air.

Note: Above question was posted by RyanP, though I have the same question.

the ratio is 3:5, so that means if you divide 120 by (3+5), you will get 15.
Now multiply 3 by 15 and 5 by 15 and you get those numbers (yes, out of thin air though with the help of some math)

Can someone please explain the reason why you can do 120 / by (3+5)? Also any alternative solution to this type of question without drawing a matrix? Thanks!

Let us say that the no of male employee is 3x.So the no of female employees would be 5x (male/Female=3x/5x=3/5)
Therefore total no of employees would be 3x+5x=8x.Also given that total no of employees is 120
so 8x=120=> x=15
hence no of male= 3x=3*15=45
and no of female = 5x=75
Hope this clears

Kudos [?]: [0], given: 7

Senior Manager
Joined: 01 Apr 2010
Posts: 297

Kudos [?]: 59 [0], given: 11

Location: Kuwait
Schools: Sloan '16 (M)
GMAT 1: 710 Q49 V37
GPA: 3.2
WE: Information Technology (Consulting)

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18 Apr 2012, 09:45
Great resource, better than another set of flashcards I recieved.

Kudos [?]: 59 [0], given: 11

Manager
Joined: 11 Jan 2011
Posts: 69

Kudos [?]: 28 [0], given: 3

GMAT 1: 680 Q44 V39
GMAT 2: 710 Q48 V40

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23 Apr 2012, 19:17
Going to try this on my Iconia 500 :D

TYVM!

Kudos [?]: 28 [0], given: 3

Intern
Joined: 04 Mar 2012
Posts: 3

Kudos [?]: [0], given: 0

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03 May 2012, 20:15
Thanks for the flashcards. so very helpful!

Kudos [?]: [0], given: 0

Intern
Joined: 25 May 2012
Posts: 4

Kudos [?]: 2 [0], given: 2

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25 May 2012, 02:56
Excellent last minute prep . Will Study and if found too good will award u additional kudos!

Keep up the good work buddy

Oh! Forgot to say thank you so much, a million thanks

Kudos [?]: 2 [0], given: 2

Intern
Joined: 20 Dec 2011
Posts: 1

Kudos [?]: [0], given: 0

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16 Jul 2012, 16:45
how can I import this into gmat app flashcards via email?

Kudos [?]: [0], given: 0

Intern
Joined: 17 May 2012
Posts: 4

Kudos [?]: [0], given: 0

Concentration: Finance, Entrepreneurship
GMAT Date: 10-20-2012
GPA: 2.89

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18 Jul 2012, 15:20

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Re: GMAT Flashcards   [#permalink] 18 Jul 2012, 15:20

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# GMAT Flashcards

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