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GRE Prep Club Team Member
Joined: 20 Feb 2017
Posts: 2506
Given Kudos: 1055
GPA: 3.39
From a bag containing 12 identical blue balls, y identical yellow ball
[#permalink]
18 Oct 2022, 07:07
18 Oct 2022, 07:07
1
Expert Reply
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Question Stats:
75% (01:25) correct
25% (02:16) wrong based on 8 sessions
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From a bag containing 12 identical blue balls, y identical yellow balls, and no other balls, one ball will be removed at random. If the probability is less than 2/5 that the removed ball will be blue, what is the least number of yellow balls that must be in the bag?
A. 17
B. 18
C. 19
D. 20
E. 21
A. 17
B. 18
C. 19
D. 20
E. 21
GRE Whiz Representative
Joined: 25 May 2022
Posts: 25
Given Kudos: 1
From a bag containing 12 identical blue balls, y identical yellow ball
[#permalink]
19 Oct 2022, 13:03
19 Oct 2022, 13:03
2
Expert Reply
The probability of picking up a blue ball = \(\frac{NumberOfBlueBalls}{NumberOfAllBalls}\) \(=\frac{12}{{12+y}}\)
We can equate it with \(\frac{2}{5}\) to get the number of yellow ball required to get a probability of \(\frac{2}{5}\).
\(\frac{NumberOfBlueBalls}{NumberOfAllBalls}\) \(=\frac{12}{{12+y}}\) = \(=\frac{2}{{5}}\)
\(Or, y = 18\)
The required number is 19.
The answer is C.
We can equate it with \(\frac{2}{5}\) to get the number of yellow ball required to get a probability of \(\frac{2}{5}\).
- The answer will be one more yellow ball
\(\frac{NumberOfBlueBalls}{NumberOfAllBalls}\) \(=\frac{12}{{12+y}}\) = \(=\frac{2}{{5}}\)
\(Or, y = 18\)
The required number is 19.
The answer is C.
gmatclubot
From a bag containing 12 identical blue balls, y identical yellow ball [#permalink]
19 Oct 2022, 13:03
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