Manhattan Prep
A jar contains 8 red marbles and \(y\) white marbles. If Joan takes 2 random marbles from the jar, is it more likely that she will have 2 red marbles than that she will have one marble of each color?
1) \(y \leq 8\)
2) \(y \geq 4\)
OA B
A jar contains 8 red marbles and \(y\) white marbles.
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Test the THRESHOLDS and try EXTREMES.AAPL wrote:Manhattan Prep
A jar contains 8 red marbles and \(y\) white marbles. If Joan takes 2 random marbles from the jar, is it more likely that she will have 2 red marbles than that she will have one marble of each color?
1) \(y \leq 8\)
2) \(y \geq 4\)
Here, the THRESHOLDS are y=8 and y=4.
Statement 1: y≤8
Case 1: 8 white marbles, 8 red marbles
P(RR) = 8/16 * 7/15 = 7/30.
P(one of each color):
P(RW) = 8/16 * 8/15 = 8/30.
Since RW can be reversed to WR, we multiply by 2:
2(8/30) = 16/30.
In this case, P(RR) < P(one of each color).
Case 2: 0 yellow marbles, 8 red marbles
Here, P(RR) = 1 and P(one of each color) = 0.
In this case, P(RR) > P(one of each color).
INSUFFICIENT.
Statement 2: y≥4
Case 1: 4 white marbles, 8 red marbles
P(RR) = 8/12 * 7/11 = 14/33.
P(one of each color):
P(RW) = 8/12 * 4/11 = 8/33.
Since RW can be reversed to WR, we multiply by 2:
2(8/33) = 16/33.
In this case, P(RR) < P(one of each color).
When y=4, P(RR) < P(one of each color).
When y=8, P(RR) < P(one of each color).
Increasing the number of yellow marbles beyond y=8 will only DECREASE the likelihood of getting RR.
Thus, P(RR) < P(one of each color).
SUFFICIENT.
The correct answer is B.
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Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
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