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Re: Jar of marbles. [#permalink]
09 Oct 2009, 14:36

1

This post received KUDOS

Bunuel wrote:

Try this one from me.

In the jar there are white and black marbles (W>0 and B>0). How many black marbles are there?

(1) There are total 101 marbles in the jar. (2) From any two marbles from the jar at least one is white.

Again, please share your way of thinking, difficulty level and quality.

Explanation of the answer to follow.

C. If white marbles were 100 and 1 Black marble, then only you get at least 1/2 while drawing 2 marbles from the jar. But you do not get answer (no. of black and white marbles) until you mix 1 and 2. _________________

Re: Jar of marbles. [#permalink]
09 Oct 2009, 14:50

Expert's post

1

This post was BOOKMARKED

GMAT TIGER wrote:

Bunuel wrote:

Try this one from me.

In the jar there are white and black marbles (W>0 and B>0). How many black marbles are there?

(1) There are total 101 marbles in the jar. (2) From any two marbles from the jar at least one is white.

Again, please share your way of thinking, difficulty level and quality.

Explanation of the answer to follow.

C. If white marbles were 100 and 1 Black marble, then only you get at least 1/2 while drawing 2 marbles from the jar. But you do not get answer (no. of black and white marbles) until you mix 1 and 2.

GMAT TIGER I didn't get the reasoning of your answer can you please specify. Anyway what's your answer, how many black marbles are there? C is incorrect.

Maybe you misunderstood the statements, or I stated them ambiguously _________________

Re: Jar of marbles. [#permalink]
09 Oct 2009, 22:58

1

This post received KUDOS

1

This post was BOOKMARKED

Bunuel wrote:

GMAT TIGER wrote:

Bunuel wrote:

Try this one from me.

In the jar there are white and black marbles (W>0 and B>0). How many black marbles are there?

(1) There are total 101 marbles in the jar. (2) From any two marbles from the jar at least one is white.

Again, please share your way of thinking, difficulty level and quality.

Explanation of the answer to follow.

C. If white marbles were 100 and 1 Black marble, then only you get at least 1/2 while drawing 2 marbles from the jar. But you do not get answer (no. of black and white marbles) until you mix 1 and 2.

GMAT TIGER I didn't get the reasoning of your answer can you please specify. Anyway what's your answer, how many black marbles are there? C is incorrect.

Maybe you misunderstood the statements, or I stated them ambiguously

I guess I overlooked - thought white for black. It is B. Given that: w>0 and b>0.

(1) Total = 101 tells nothing about individusl msrbles. (2) If any two marbles from the jar are drawn, at least one is a white. That means black cannot be more than 1. so Black = 1 irrespective of whites.

Another good one. Are you gmat instructer/question writer? _________________

Re: Jar of marbles. [#permalink]
09 Oct 2009, 23:21

Expert's post

1

This post was BOOKMARKED

Yes you're right. Answer B. +1.

Thats what I like in this problem: the number of black marbles are in no connection with total number of marbles. Simple logic.

I'm neither gmat instructor nor question writer, I'm just preparing for GMAT. Just found that composing questions helps me to understand better the logic of the quant problems in GMAT. _________________

Re: Jar of marbles. [#permalink]
10 Oct 2009, 02:59

Awesome question.. I arrived at E. Line of reasoning: At least one white means that number of white > 50% of total...however even after combining we cannot tell the exact number of whites..it can be 60%(Total) or 70%(Total)..

The catch is the word "any" in B. If ANY two marbles are picked and if black can be 1(max) means, there is only one black !!!!

Re: Jar of marbles. [#permalink]
10 Oct 2009, 08:10

Expert's post

Economist wrote:

Awesome question.. I arrived at E. Line of reasoning: At least one white means that number of white > 50% of total...however even after combining we cannot tell the exact number of whites..it can be 60%(Total) or 70%(Total)..

The catch is the word "any" in B. If ANY two marbles are picked and if black can be 1(max) means, there is only one black !!!!

Thanks Economist, I knew that this trap ("any" in second statement) would work.

And yes answer is 1 black marble, (2) alone is sufficient. B. _________________

Re: Jar of marbles. [#permalink]
10 Oct 2009, 08:30

I guess thats the best way to practice gmat.

Your questions are perfectly up to the real gmat standard.

lol................ +1

Bunuel wrote:

Yes you're right. Answer B. +1.

Thats what I like in this problem: the number of black marbles are in no connection with total number of marbles. Simple logic.

I'm neither gmat instructor nor question writer, I'm just preparing for GMAT. Just found that composing questions helps me to understand better the logic of the quant problems in GMAT.

Re: Jar of marbles. [#permalink]
05 Jan 2010, 12:24

1

This post received KUDOS

Bunuel wrote:

Yes you're right. Answer B. +1. I'm neither gmat instructor nor question writer, I'm just preparing for GMAT. Just found that composing questions helps me to understand better the logic of the quant problems in GMAT.

Awesome question.....! U preparing for GMAT! U mite end up getting 900 score in it :D LOL!! _________________

Cheers! JT........... If u like my post..... payback in Kudos!!

|Do not post questions with OA|Please underline your SC questions while posting|Try posting the explanation along with your answer choice| |For CR refer Powerscore CR Bible|For SC refer Manhattan SC Guide|

Re: In the jar there are white and black marbles (W>0 and B>0). [#permalink]
19 Jan 2014, 05:32

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email. _________________

Re: In the jar there are white and black marbles (W>0 and B>0). [#permalink]
06 Feb 2014, 23:43

Goodday Bunuel Can you please explain why it is B??... Option B says : "From any two marbles from the jar at least one is white"...This means 1 or both are white but the question asks "how many?"....I am stuck here Thanks in advance..

Re: In the jar there are white and black marbles (W>0 and B>0). [#permalink]
25 Feb 2014, 10:18

If there were 2 black balls, there is a chance of picking up two black balls. But the second statement states that from any two marbles from the jar AT LEAST 1 is white meaning there is only 1 black ball in the jar.

srinjoy28 wrote:

Goodday Bunuel Can you please explain why it is B??... Option B says : "From any two marbles from the jar at least one is white"...This means 1 or both are white but the question asks "how many?"....I am stuck here Thanks in advance..

Re: In the jar there are white and black marbles (W>0 and B>0). [#permalink]
25 Feb 2014, 10:50

2

This post received KUDOS

Bunuel wrote:

In the jar there are white and black marbles (W>0 and B>0). How many black marbles are there?

(1) There are total 101 marbles in the jar. (2) From any two marbles from the jar at least one is white.

My take is B.

consider 1 alone) it tells us nothing about the number of white or black marbles in particular.

consider 2 alone) consider the total number of marbles to be 5 (for simplicity, it can be extended up to infinite number of marbles) let the 5 marbles be --> A,B,C,D and E. now option 2 says, if we pick any 2 marbles...at least 1 of them would be white. if we form every possible group of 2 from these, we get - AB,AC,AD,AE,BC,BD,BE,CD,CE and DE. (10 groups, which is nothing but C(5,2)) since at least one of any two is white, we can safely say A,B,C and D are definitely white. E can be either black or white. but since our fact statement says W>0 and B>0; E has to be a black marble. Hence, with statement 2 alone we can determine the number of black marbles...which would always be 1.

Re: In the jar there are white and black marbles (W>0 and B>0). [#permalink]
15 Apr 2015, 03:39

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email. _________________

Re: In the jar there are white and black marbles (W>0 and B>0). [#permalink]
26 Apr 2015, 22:36

2

This post received KUDOS

Bunuel you were preparing for GMAT!!!!!!(P.S i just came to know that) sorry mate but there is no school for you not atleast on this planet my advice is please look in some other galaxy. For god's sake please tell me who can teach bunuel anything hahahaha. now i know from where the real competition comes in this exam. envy you bunuel

gmatclubot

Re: In the jar there are white and black marbles (W>0 and B>0).
[#permalink]
26 Apr 2015, 22:36

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