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Bowls X and Y each contained exactly 2 jelly beans, each of

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Status: May The Force Be With Me (D-DAY 15 May 2012)
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Bowls X and Y each contained exactly 2 jelly beans, each of  [#permalink]

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New post 08 Apr 2012, 08:44
3
5
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

64% (01:31) correct 36% (03:13) wrong based on 670 sessions

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Project DS Butler: Day 26: Data Sufficiency (DS52)


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Bowls X and Y each contained exactly 2 jelly beans, each of which was either red or black. One of the jelly beans in bowl X was exchanged with one of the jelly beans in bowl Y. After the exchange, were both of the jelly beans in bowl X black?

(1) Before the exchange, bowl X contained 2 black jelly beans.
(2) After the exchange, bowl Y contained 1 jelly bean of each color.

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Re: Bowls X and Y each contained exactly 2 jelly beans, each of  [#permalink]

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New post 08 Apr 2012, 09:13
1
boomtangboy wrote:
Bowls X and Y each contained exactly 2 jelly beans, each of which was either red or black. One of the jelly beans in bowl X was exchanged with one of the jelly beans in bowl Y. After the exchange, were both of the jelly beans in bowl X black?

(1) Before the exchange, bowl X contained 2 black jelly beans.
(2) After the exchange, bowl Y contained 1 jelly bean of each color.


Consider two cases for (1)+(2):

Initially X={BB} and Y={BR} --> B was exchanged with B --> X={BB} and Y={BR}: answer is YES;
Initially X={BB} and Y={RR} --> B was exchanged with R --> X={BR} and Y={BR}: answer is NO.

Answer: E.
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Re: Bowls X and Y each contained exactly 2 jelly beans, each of  [#permalink]

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New post 19 Nov 2013, 20:48
1
1) NS, because it gives no information on X after the exchange.
2) NS, because the initial for both X and Y could be the following:
X=RR Y=BB
X=RB Y=BB

1+2) NS
Case 1)
Before
X=BB Y=RR

After
Y=BR Y=RB

Case 2)
Before
X=BB Y=RB

After
X=BB Y=RB
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Re: Bowls X and Y each contained exactly 2 jelly beans, each of  [#permalink]

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New post 24 Dec 2013, 01:21
I used very simple cases and got to the conclusion real quick.
Before
X=RR Y=RR

After
Y=RR Y=RR

Next Case
Before
X=BB Y=RR

After
X=BR Y=RB
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Re: Bowls X and Y each contained exactly 2 jelly beans, each of  [#permalink]

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New post 27 Jan 2015, 18:20
Question: how do you know they are not "exclusive". I misunderstood the question as meaning that there are 2 black and 2 reds, and thus had everything wrong. What clue can you pick up to know that there can be any combination of colors?
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Re: Bowls X and Y each contained exactly 2 jelly beans, each of  [#permalink]

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New post 11 Jul 2017, 21:32
boomtangboy wrote:
Bowls X and Y each contained exactly 2 jelly beans, each of which was either red or black. One of the jelly beans in bowl X was exchanged with one of the jelly beans in bowl Y. After the exchange, were both of the jelly beans in bowl X black?

(1) Before the exchange, bowl X contained 2 black jelly beans.
(2) After the exchange, bowl Y contained 1 jelly bean of each color.


This question tests the general ability to think of counterexamples

It cannot be (1) alone because before exchange X=BB with Y=RR and Y=BR give different results for X
It cannot be (2) alone because after exchange Y=BR can come from X= BB with Y=RR and Y=BR and can give different results for X
It cannot be (1) and (2) together also because before exchange X=BB with Y=RR and Y=BR can give different results for X with Y=BR after exchange

So the answer is E

Note: Try to use the same counter example as far as possible.
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Bowls X and Y each contained exactly 2 jelly beans, each of  [#permalink]

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New post 02 Dec 2018, 02:47
Bowls X and Y each contained exactly 2 jelly beans, each of which was either red or black. One of the jelly beans in bowl X was exchanged with one of the jelly beans in bowl Y. After the exchange, were both of the jelly beans in bowl X black?

(1) Before the exchange, bowl X contained 2 black jelly beans.
Before the exchange cannot tell anything regarding after exchange. Insufficient.

(2) After the exchange, bowl Y contained 1 jelly bean of each color.
After exchange, Y (RB), but X could be (RR) (BB) (RB). Not unique, insufficient.

(1) & (2)
If before exchange, bowl X is (BB), and Y can be (BR) (BB) (RR)
After exchange, bowl X can be (BR) (BB). No unique, Insufficient
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Bowls X and Y each contained exactly 2 jelly beans, each of &nbs [#permalink] 02 Dec 2018, 02:47
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Bowls X and Y each contained exactly 2 jelly beans, each of

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