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Containers A and B each contain 8 gold coins, 12 silver coins, and not

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Joined: 09 May 2017
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Containers A and B each contain 8 gold coins, 12 silver coins, and not  [#permalink]

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Updated on: 29 Jul 2017, 06:22
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63% (02:06) correct 37% (02:37) wrong based on 106 sessions

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Containers A and B each contain 8 gold coins, 12 silver coins, and nothing else. Container C contains 1 gold coin, 4 silver coins, and nothing else. A container is chosen at random and then a coin is chosen at random from that container. What is the probability that the chosen coin is silver?

A. 4/15

B. 2/5

C. 7/15

D. 3/5

E. 2/3

Originally posted by 3newton on 29 Jul 2017, 01:58.
Last edited by chetan2u on 29 Jul 2017, 06:22, edited 2 times in total.
updated the OA
Current Student
Joined: 09 May 2017
Posts: 15
WE: Information Technology (Consulting)
Re: Containers A and B each contain 8 gold coins, 12 silver coins, and not  [#permalink]

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29 Jul 2017, 02:02
1
Is this approach correct?

(1/3 x 0/8) + (1/3 x 12/20) + (1/3 x 4/5) = 7/15

i.e. Prob of selecting that box X Probability of getting a silver in that box

summation of this for all 3 boxes
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Joined: 21 Jun 2017
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GMAT 1: 750 Q50 V41
Re: Containers A and B each contain 8 gold coins, 12 silver coins, and not  [#permalink]

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29 Jul 2017, 02:15
1
Does anyone think the question is quite misleading? Containers A and B "each" contains 8 gold coins, 12 silver coins, and nothing else. Does this not indicate that A contains 8G and 12S and that B contains the same coins as A? Only after I finish my calculation that I realized this way was wrong.
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GMAT 1: 640 Q49 V29
Re: Containers A and B each contain 8 gold coins, 12 silver coins, and not  [#permalink]

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29 Jul 2017, 02:38
3newton wrote:
Is this approach correct?

(1/3 x 0/8) + (1/3 x 12/20) + (1/3 x 4/5) = 7/15

i.e. Prob of selecting that box X Probability of getting a silver in that box

summation of this for all 3 boxes

Hey 3newton,
Can you please tell why you have multiplied 0/3. Rest of he things are clear.

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Manager
Joined: 02 Nov 2015
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GMAT 1: 640 Q49 V29
Re: Containers A and B each contain 8 gold coins, 12 silver coins, and not  [#permalink]

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29 Jul 2017, 02:39
Rather I would have gone for 1/3(12/20+12/20+4/5).
Thus would have led to 2/3.
Ans E.

Please correct my understanding of needed.

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Re: Containers A and B each contain 8 gold coins, 12 silver coins, and not  [#permalink]

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29 Jul 2017, 06:06
kumarparitosh123 wrote:
Rather I would have gone for 1/3(12/20+12/20+4/5).
Thus would have led to 2/3.
Ans E.

Please correct my understanding of needed.

Sent from my Lenovo TAB S8-50LC using GMAT Club Forum mobile app

The line "Containers A and B each contain 8 gold coins, 12 silver coins, and nothing else" is quite misleading here.
What it actually wants to say is that Container A contains 8 Gold coins and nothing else, and Container B contains 12 Silver coins and nothing else.

Seems to be a poor quality question..
Math Expert
Joined: 02 Aug 2009
Posts: 7589
Re: Containers A and B each contain 8 gold coins, 12 silver coins, and not  [#permalink]

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29 Jul 2017, 06:21
3newton wrote:
Containers A and B each contain 8 gold coins, 12 silver coins, and nothing else. Container C contains 1 gold coin, 4 silver coins, and nothing else. A container is chosen at random and then a coin is chosen at random from that container. What is the probability that the chosen coin is silver?

A. 4/15

B. 2/5

C. 7/15

D. 3/5

E. 2/3

Hi...
the way Q is written, answer is clearly E.....

Q means BOTH A and B contain 8G and 12S. container C contains 1G and 4S..

Now how have you interpreted it as 0 silver in A is wrong...

Any of three can be choosen, so choosing each means probability of 1/3..

total $$\frac{1}{3}*\frac{12}{20}*2+\frac{1}{3}*\frac{4}{5} = \frac{2}{3}$$

E
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Containers A and B each contain 8 gold coins, 12 silver coins, and not  [#permalink]

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29 Jul 2017, 06:22
1
3newton wrote
Quote:
Containers A and B each contain 8 gold coins, 12 silver coins, and nothing else. Container C contains 1 gold coin, 4 silver coins, and nothing else. A container is chosen at random and then a coin is chosen at random from that container. What is the probability that the chosen coin is silver?

A. 4/15

B. 2/5

C. 7/15

D. 3/5

E. 2/3

K_Leon wrote:
Does anyone think the question is quite misleading? Containers A and B "each" contains 8 gold coins, 12 silver coins, and nothing else. Does this not indicate that A contains 8G and 12S and that B contains the same coins as A? Only after I finish my calculation that I realized this way was wrong.

Yes. I remain confused. I got the correct answer through no fault of my own. I guessed.

A thorough discussion of "each" and "both" belongs in SC, so I'll keep it as short as I can. One hat I wear is editor of English prose.

"Each" refers to every one of any number, when considered individually or separately. "Both" refers to two, taken together. "Each," almost always, is a singular subject (hence singular verb). "Both" is a plural subject. The prompt's plural verb "contain" implies both. ????

"Each" should be used to emphasize the individuality of separate conditions. "The company gave both women $100,000." Unclear. Corrected: "The company gave each woman$100,000." (The women did not split the $100,000.) Clarity would be simple to achieve. "Jars A and B both contain ..." Or "Jars A and B contain, respectively, 8 gold and 12 silver coins." I still can't figure out how, in 3newton 's response, A has 0 silver coins of 8 total but B has 12 silver coins of 20 total. Doesn't A also have 20 coins? If A = 8 total and B = 12 total, I think the equation is (1/3 * 0/8) + (1/3 * 12/12) + (1/3 * 4/5) = 3/5 kumarparitosh123 , I think you are correct. If A and B both have 8 gold and 12 silver coins, I agree that the equation is (1/3 * 12/20) + (1/3 * 12/20) + (1/3 * 4/5) = 2/3 That said, if words were clear and OA were different, the content would be interesting. 3newton , are you sure the OA is correct? chetan2u , I disagree respectfully. I don't think there's anything clear about it. Both answers D and E are defensible. _________________ Listen, are you breathing just a little, and calling it a life? -- Mary Oliver For practice SC questions with official explanations that were posted and moderated by the SC Team, go to SC Butler here: https://gmatclub.com/forum/project-sc-butler-get-2-sc-questions-everyday-281043.html Math Expert Joined: 02 Aug 2009 Posts: 7589 Containers A and B each contain 8 gold coins, 12 silver coins, and not [#permalink] Show Tags 29 Jul 2017, 06:33 genxer123 wrote: 3newton wrote Quote: Containers A and B each contain 8 gold coins, 12 silver coins, and nothing else. Container C contains 1 gold coin, 4 silver coins, and nothing else. A container is chosen at random and then a coin is chosen at random from that container. What is the probability that the chosen coin is silver? A. 4/15 B. 2/5 C. 7/15 D. 3/5 E. 2/3 K_Leon wrote: Does anyone think the question is quite misleading? Containers A and B "each" contains 8 gold coins, 12 silver coins, and nothing else. Does this not indicate that A contains 8G and 12S and that B contains the same coins as A? Only after I finish my calculation that I realized this way was wrong. Yes. I remain confused. I got the correct answer through no fault of my own. I guessed. A thorough discussion of "each" and "both" belongs in SC, so I'll keep it as short as I can. One hat I wear is editor of English prose. "Each" refers to every one of any number, when considered individually or separately. "Both" refers to two, taken together. "Each," almost always, is a singular subject (hence singular verb). "Both" is a plural subject. The prompt's plural verb "contain" implies both. ???? "Each" should be used to emphasize the individuality of separate conditions. "The company gave both women$100,000." Unclear. Corrected: "The company gave each woman $100,000." (The women did not split the$100,000.)

Clarity would be simple to achieve. "Jars A and B both contain ..." Or "Jars A and B contain, respectively, 8 gold and 12 silver coins."

I still can't figure out how, in 3newton 's response, A has 0 silver coins of 8 total but B has 12 silver coins of 20 total. Doesn't A also have 20 coins?

If A = 8 total and B = 12 total, I think the equation is (1/3 * 0/8) + (1/3 * 12/12) + (1/3 * 4/5) = 3/5

kumarparitosh123 , I think you are correct.

If A and B both have 8 gold and 12 silver coins, I agree that the equation is (1/3 * 12/20) + (1/3 * 12/20) + (1/3 * 4/5) = 2/3

That said, if words were clear and OA were different, the content would be interesting. 3newton , are you sure the OA is correct?

chetan2u ,I disagree respectfully. I don't think there's anything clear about it. Both answers D and E are defensible.

Hi,

Disagreement is always good, and with respect is even better .
So I may agree with what you have written but not with D as answer in any way, neither mathematically or grammatically..

an error of contain/contains is perfectly fine in the forum, may not be in actuals. but there too it would mean the same.

say if I take what you say --
Quote:
Containers A and B each contain 8 gold coins, 12 silver coins, and nothing else. could mean the equation is (1/3 * 0/8) + (1/3 * 12/12) + (1/3 * 4/5) = 3/5

so A has 8 gold coins , B has 12 silver BUT WHO has " nothing else"
so this solution does not stand grammatically too..
E is the only possible answer.
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Containers A and B each contain 8 gold coins, 12 silver coins, and not  [#permalink]

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29 Jul 2017, 08:21
chetan2u wrote:
genxer123 wrote:

chetan2u ,I disagree respectfully. I don't think there's anything clear about it. Both answers D and E are defensible.

Hi,

Disagreement is always good, and with respect is even better .
So I may agree with what you have written but not with D as answer in any way, neither mathematically or grammatically..

an error of contain/contains is perfectly fine in the forum, may not be in actuals. but there too it would mean the same.

say if I take what you say --
Quote:
Containers A and B each contain 8 gold coins, 12 silver coins, and nothing else. could mean the equation is (1/3 * 0/8) + (1/3 * 12/12) + (1/3 * 4/5) = 3/5

so A has 8 gold coins , B has 12 silver BUT WHO has " nothing else"
so this solution does not stand grammatically too..
E is the only possible answer.

"A has 8 gold coins, B has 12 silver coins, and [in each there is] nothing else."

That's correct, grammatically.
_________________
Listen, are you breathing just a little, and calling it a life?
-- Mary Oliver

For practice SC questions with official explanations that were posted and moderated by the SC Team,
go to SC Butler here: https://gmatclub.com/forum/project-sc-butler-get-2-sc-questions-everyday-281043.html
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Posts: 351
Re: Containers A and B each contain 8 gold coins, 12 silver coins, and not  [#permalink]

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29 Aug 2017, 00:20
I did a more 'one at a time' probability and added them up:
--> prob of container: 1/3 (choosing one out of 3 containers A,B,C)
--> prob of silver per container --> if either A and B --> then 1/12
--> if either C --> then 1/4
Prob of all silver --> 1/4 + 1/16 = 1/3
--> Prob of silver and container =1/3 + 1/3 -->2/3 (E)
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Re: Containers A and B each contain 8 gold coins, 12 silver coins, and not  [#permalink]

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29 Aug 2017, 00:24
1
Also, I do notice an error in phrasing 'each contain' -- since I read container A and B; it skipped my attention. (this is not advisable anyway in GMAT exam where every word is important) . Now it would complicate matters because it means A and B total would be 16 gold and 24 silver coins --> I think this question needs to be re-phrased
Re: Containers A and B each contain 8 gold coins, 12 silver coins, and not   [#permalink] 29 Aug 2017, 00:24
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