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A jar is filled with 60 marbles. All the marbles in the jar

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by BTGmoderatorAT » Sun Jan 07, 2018 9:07 am
A jar is filled with 60 marbles. All the marbles in the jar are either red or green. What is the smallest number of marbles that must be drawn from the jar in order to be certain that a red marble is drawn?

(1) The ratio of red marbles to green marbles is 2 : 1.
(2) There are 20 green marbles in the jar.

What's the best way to determine whether statement 1 is sufficient?
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Source: — Data Sufficiency |

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by Jay@ManhattanReview » Mon Jan 08, 2018 5:32 am
ardz24 wrote:A jar is filled with 60 marbles. All the marbles in the jar are either red or green. What is the smallest number of marbles that must be drawn from the jar in order to be certain that a red marble is drawn?

(1) The ratio of red marbles to green marbles is 2 : 1.
(2) There are 20 green marbles in the jar.

What's the best way to determine whether statement 1 is sufficient?
(1) The ratio of red marbles to green marbles is 2 : 1.

=> Number of red marbles = [2 / (2 + 1)]*60 = 2/3 * 6 = 40.

Thus, the smallest number to be drawn from the jar is 40 + 1 = 41 to be 100% certain that a red marble is drawn.

(2) There are 20 green marbles in the jar.

=> Number of red marbles = 60 - 20 = 40.

Thus, the smallest number to be drawn from the jar is 40 + 1 = 41 to be 100% certain that a red marble is drawn.

The correct answer: D

Hope this helps!

-Jay
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