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

Question

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.

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

DS16402.01

Bunuel · Accepted Answer

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.

TooLong150 · Answer

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

thinkbigthink800 · Answer

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

SVaidyaraman · Answer

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.

kookies · Answer

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.

(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

reynaldreni · Answer

(1) Before the exchange, bowl X contained 2 black jelly beans.
case#1
Before X  Y 
After X  Y 
After the exchange, were both of the jelly beans in bowl X black? --> NO
case#2
Before X  Y 
After X  Y 
After the exchange, were both of the jelly beans in bowl X black? --> YES

Insufficient

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

We do not know anything about bowl X
Insufficient

(1)+(2)
case#1
Before X  Y 
After X  Y 
After the exchange, were both of the jelly beans in bowl X black? --> NO
case#2
Before X  Y 
After X  Y 
After the exchange, were both of the jelly beans in bowl X black? --> YES

Insufficient

OA <-- E

Basshead · Answer

Each bowl can have (R,B), (B,B), (R,R)

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.

(1) Before the exchange, bowl X contained 2 black jelly beans.

No information on the jelly beans in Bowl Y. INSUFFICIENT.

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

No information on jelly bowls in Bowl X before the exchange. INSUFFICIENT.

(1&2) Bowl X contained (B, B) before the exchange. Bowl Y contained (B, R) after the exchange. However, we don't know what Bowl Y originally had. Bowl Y could have had (R, R) or (B, B), giving X either black or red. INSUFFICIENT.

Answer is E.

Shashwatrakesh · Answer

Bowls X and Y each contained exactly 2 jelly beans, each of which was either red or black -- the statement clearly mentions that each of the set of 2 jelly beans is either red or black. How is there a possibility of red, black in a single bowl.
Please correct me if my interpretation is wrong

dylanl1218 · Answer

In case anyone else is having trouble with this one, here's a visualization for statements (1) and (2) together:

Crytiocanalyst · Answer

The key to solving the question is getting all the combinations correct

(1) Before the exchange, bowl X contained 2 black jelly beans.
This could to 3 possibilities in the y bag
Clearly insufficient

(2) After the exchange, bowl Y contained 1 jelly bean of each color.
This as from the above argument leads to 3 possibilities
in the X bag
INsuff

Even when 1 and 2 is combined we get
either both black or 1 black 1 red in bag

INSUFFICIENT
HEnce IMO E

Iotaa · Answer

S1. Whether the exchanged jelly bean from Y to X is black or red? not sure.
 Sufficient

S2. No information to conclude which color jelly bean is transferred from Y to X.  Sufficient

S1 + S2
Still not sufficient. Hence E

pearrrrrrr · Answer

Hi  Bunuel

If the question specified “there are equal number of each color”, the answer would be D. Correct?

Posted from my mobile device

Bunuel · Answer

_____________
Yes, correct.

bumpbot · Answer

Automated notice from GMAT Club BumpBot: 

A member just gave Kudos to this thread, showing it’s still useful. I’ve bumped it to the top so more people can benefit. Feel free to add your own questions or solutions.

 This post was generated automatically.

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

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards

GMAT Data Sufficiency (DS) Questions

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

Prep Toolkit

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards