雷哥网GMAT-【OG20-P274-245题】Each of the marbles in a jar is either red or whit_OG17新题

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【OG20-P274-245题】

Each of the marbles in a jar is either red or white or blue. If one marble is to be selected at random from the jar, what is the probability that the marble will be blue?

(1) There are a total of 24 marbles in the jar, 8 of which are red.

(2) The probability that the marble selected will be white is 1/2.

A

Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
分析A选项
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B

Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
分析B选项
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C

BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
分析C选项
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D

EACH statement ALONE is sufficient.
分析D选项
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E

Statements (1) and (2) TOGETHER are NOT sufficient.
分析E选项
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当前版本由 Helen 更新于2018-09-19 14:02:47 感谢由 Helen 对此题目的解答所做出的贡献。

条件1：blue有多少个未知，不充分
条件2：同理，不充分
结合：blue=24-12-8=4，概率=4/24=1/6，充分

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11

We need to find the ratio (no. of blue marbles/total marbles). (1) 8 are red. So, 16 are either blue or white. This could mean 0 blue, 16 white or any number for blue upto 16, with 16-blue number of whites. Not sufficient. (2) probability of white is 1/2. So, probability of (blue or red) is 1/2. Now, we don't know the probability of red, so we can't find that of blue. Not sufficient. (1) and (2) together - probability of white = 1/2. We also know from (1) that there are 24 marbles in all. So, there are 12 white marbles (since 12/24 = 1/2). Out of the remaining, 8 are red, so 4 must be blue. Given this, we can find the probability of blue marbles as 4/24 = 1/6. Hence, BOTH TOGETHER ARE SUFFICIENT.

0 0 回复 2017-11-19 05:22:22
多啦A沫

有人能给详解吗？

0 0 回复 2017-06-19 14:45:37
多啦A沫回复多啦A沫

不用给了，想出来了。。。

0 0 回复 2017-06-19 15:35:24