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# GMAT Flashcards

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Intern
Joined: 20 Feb 2012
Posts: 11

Kudos [?]: 8 [0], given: 0

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11 Mar 2012, 10:57
Could you explain part of the following problem?

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.

Kudos [?]: 8 [0], given: 0

Manager
Joined: 28 Apr 2011
Posts: 176

Kudos [?]: 10 [0], given: 6

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19 Mar 2012, 18:59
Thanks for this nice thread guys.......Indeed its one of the best resources for GMAT.

Kudos [?]: 10 [0], given: 6

Intern
Joined: 25 Jun 2011
Posts: 47

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

Location: Sydney

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23 Mar 2012, 19:02
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)

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

Founder
Joined: 04 Dec 2002
Posts: 16305

Kudos [?]: 29983 [0], given: 5452

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

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23 Mar 2012, 19:08
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?
Attachments

stats-flashcards.gif [ 52.46 KiB | Viewed 5407 times ]

_________________

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 [?]: 29983 [0], given: 5452

Founder
Joined: 04 Dec 2002
Posts: 16305

Kudos [?]: 29983 [0], given: 5452

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

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23 Mar 2012, 19:11
RyanP wrote:
Could you explain part of the following problem?

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.

Errrr.... 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)
_________________

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 [?]: 29983 [0], given: 5452

Intern
Joined: 25 Jun 2011
Posts: 47

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

Location: Sydney

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23 Mar 2012, 19:59
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

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

Intern
Joined: 25 Jun 2011
Posts: 47

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

Location: Sydney

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23 Mar 2012, 23:44
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, 00:15
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: 16305

Kudos [?]: 29983 [0], given: 5452

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

### Show Tags

24 Mar 2012, 13:09
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 [?]: 29983 [0], given: 5452

Founder
Joined: 04 Dec 2002
Posts: 16305

Kudos [?]: 29983 [0], given: 5452

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

### Show Tags

24 Mar 2012, 13:21
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 [?]: 29983 [0], given: 5452

Founder
Joined: 04 Dec 2002
Posts: 16305

Kudos [?]: 29983 [0], given: 5452

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

### Show Tags

24 Mar 2012, 13:25
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 [?]: 29983 [0], given: 5452

Intern
Joined: 12 Oct 2008
Posts: 13

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

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27 Mar 2012, 08:20
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

Intern
Joined: 12 Oct 2008
Posts: 13

Kudos [?]: 4 [1], given: 2

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27 Mar 2012, 10:08
1
KUDOS
Page 51 and 52 are repeats, CG slide 8,9,10 from page 49 and 50.

Kudos [?]: 4 [1], given: 2

Founder
Joined: 04 Dec 2002
Posts: 16305

Kudos [?]: 29983 [0], given: 5452

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

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27 Mar 2012, 10:12
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 [?]: 29983 [0], given: 5452

Founder
Joined: 04 Dec 2002
Posts: 16305

Kudos [?]: 29983 [0], given: 5452

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

### Show Tags

27 Mar 2012, 10:22
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 [?]: 29983 [0], given: 5452

Founder
Joined: 04 Dec 2002
Posts: 16305

Kudos [?]: 29983 [0], given: 5452

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

### Show Tags

27 Mar 2012, 10:27
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 [?]: 29983 [0], given: 5452

Intern
Joined: 25 Jun 2011
Posts: 47

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

Location: Sydney

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28 Mar 2012, 16:40
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, 06:47
Wow I found this to be very useful if you tackle this before taking on the OG you'll be surprised on your results!!

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Manager
Joined: 06 Jul 2011
Posts: 213

Kudos [?]: 72 [0], given: 39

Location: Accra, Ghana

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09 Apr 2012, 01:48
I now have some resources that I can constantly look over daily to remember the stuff I should be learning.

Kudos [?]: 72 [0], given: 39

Manager
Status: I will be back!
Joined: 13 Feb 2012
Posts: 67

Kudos [?]: 76 [1], given: 38

Location: India

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10 Apr 2012, 01:23
1
KUDOS
Thanks for the flashcards. These are awesome.

Just found out one issue in flashcard no. 42.
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Re: GMAT Flashcards   [#permalink] 10 Apr 2012, 01:23

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# GMAT Flashcards

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