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

Question

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.

Sutirtha · Answer

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

HKD1710 · Answer

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.

HKD1710 · Answer

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

roadrunner · Answer

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

matthewsmith_89 · Answer

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

Fdambro294 · Answer

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

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

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

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