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If a barrel contains only red and white balls, how many red balls are

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Bunuel
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If a barrel contains only red and white balls, how many red balls are [#permalink] New post   27 Mar 2017, 04:59
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If a barrel contains only red and white balls, how many red balls are in the barrel?

(1) The probability of pulling out a red ball with one random selection is 2/7.
(2) The probability of pulling out a white ball with one random selection is 5/7.
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Sutirtha
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Re: If a barrel contains only red and white balls, how many red balls are [#permalink] New post   27 Mar 2017, 07:26
Let number of Red and White balls be R and W.

Then as per (1) R/(R+W) = 2/7 . Simplify and we get 5R=2W.--> Insufficient to deduce no of red balls.

Similarly as per St (2) W/W+R= 5/7 which is basically 1-R/R+W which also gives 5R=2W.----> Insufficient

Combining (1) and (2) Insufficient

Answer should be (E).

Please post the OA as per scheduled
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Re: If a barrel contains only red and white balls, how many red balls are [#permalink] New post   27 Mar 2017, 10:59
Probability is the ratio.

stmt-1: The probability of pulling out a red ball with one random selection is 2/7

P(R) = 2/7 could be 4/14 or 6/21 and this means:
red balls could be 2 when total balls are 7 OR
red balls could be 4 when total balls are 14 OR
red balls could be 6 when total balls are 21

insufficient.

stmt-2: The probability of pulling out a white ball with one random selection is 5/7.

P(W) = 5/7 then
P(R) = 1- P(W)
P(R) = 1- 5/7 i.e. 2/7

So stmt-2 is same as stmt-1.

Insufficient.

There is no need to combine when both the stmt-1 and stmt-2 are same.

IMO Answer should be E.
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Re: If a barrel contains only red and white balls, how many red balls are [#permalink] New post   27 Mar 2017, 11:03
Sutirtha wrote:
Let number of Red and White balls be R and W.

Then as per (1) R/(R+W) = 2/7 . Simplify and we get 5R=2W.--> Insufficient to deduce no of red balls.

Similarly as per St (2) W/W+R= 5/7 which is basically 1-R/R+W which also gives 5R=2W.----> Insufficient

Combining (1) and (2) Insufficient

Answer should be (E).

Please post the OA as per scheduled


Hi Sutirtha,

In the question posted, Please notice "The OA will be automatically revealed on Monday 3rd of April 2017 04:59:55 AM Pacific Time Zone".

Answer is revealed automatically on the specified time. so rest assured :)
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Re: If a barrel contains only red and white balls, how many red balls are [#permalink] New post   27 Mar 2017, 11:12
Bunuel wrote:
If a barrel contains only red and white balls, how many red balls are in the barrel?

(1) The probability of pulling out a red ball with one random selection is 2/7.
(2) The probability of pulling out a white ball with one random selection is 5/7.


1. P(Red) = 2x/7x --> As x can take multiple values --> Insufficient
2. P(White) = 5x/7x --> for above mentioned reason, this statement is also insufficient

1&2 --> As the barrel contains only red and white balls, combining both statement does not reveal new information to help derive the value of x ==> Insufficient

Ans. E
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matthewsmith_89
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If a barrel contains only red and white balls, how many red balls are [#permalink] New post   27 Mar 2017, 20:04
1 is insufficient. Just because it provides the probability of red ball doesn't answer the question. There could have been 20, 200 or so on red balls.
2 is also insufficient. Just because it provides the probability of white ball doesn't answer the question again. There could have been 50 500 or so on red ball.

Combine 1 & 2 - still insufficient.

Answer: E
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Re: If a barrel contains only red and white balls, how many red balls are [#permalink] New post   31 Dec 2021, 20:24
Ratio Value information alone is never enough to determine the unique actual value.

Case 1 red = 2 and white = 5

Case 2: red = 4 and white = 10

Either case satisfies both conditions.

E

Bunuel wrote:
If a barrel contains only red and white balls, how many red balls are in the barrel?

(1) The probability of pulling out a red ball with one random selection is 2/7.
(2) The probability of pulling out a white ball with one random selection is 5/7.


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Re: If a barrel contains only red and white balls, how many red balls are [#permalink]
31 Dec 2021, 20:24
Moderator:
Bunuel
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