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A jar contains 20 marbles: 4 red, 6 white and 10 blue
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06 Nov 2016, 13:11
06 Nov 2016, 13:11
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Question Stats:
38% (01:05) correct
61% (01:15) wrong based on 59 sessions
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A jar contains 20 marbles: 4 red, 6 white and 10 blue. If you remove marbles one at a time, randomly, what is the minimum number that must be removed to be certain that you have at least 2 marbles of each colour?
A. 6
B. 10
C. 12
D. 16
E. 18
A. 6
B. 10
C. 12
D. 16
E. 18
Re: A jar contains 20 marbles: 4 red, 6 white and 10 blue
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06 Nov 2016, 13:40
06 Nov 2016, 13:40
5
Expert Reply
Here we have 10 Blue 6 White and 4 Red. The worst case scenario you pull all white and blue before you pull 2 red.
Hence minimum number of marbles you need the pull is all 10 white, 6 White and 2 Red.
Number of marbles to be removed = \(10 + 6 + 2\) = \(18\)
Hence minimum number of marbles you need the pull is all 10 white, 6 White and 2 Red.
Number of marbles to be removed = \(10 + 6 + 2\) = \(18\)
General Discussion
Target Test Prep Representative
Joined: 09 May 2016
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Re: A jar contains 20 marbles: 4 red, 6 white and 10 blue
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06 May 2018, 16:39
06 May 2018, 16:39
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Expert Reply
SJ wrote:
A jar contains 20 marbles: 4 red, 6 white and 10 blue. If you remove marbles one at a time, randomly, what is the minimum number that must be removed to be certain that you have at least 2 marbles of each colour?
A. 6
B. 10
C. 12
D. 16
E. 18
A. 6
B. 10
C. 12
D. 16
E. 18
Assume the worst case scenario, that is, you remove all 10 blue marbles and all 6 white marbles; you still don’t have any marbles in red. However, if you remove 2 more marbles (and they must be red), then you will have at least 2 marbles of each color. Therefore, you need to remove a total of 18 marbles to ensure you will have at least 2 marbles of each color.
Answer: E
