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from a bag containing 12 identical blue balls, y identical

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Manager
Joined: 05 Jul 2006
Posts: 197
from a bag containing 12 identical blue balls, y identical [#permalink]

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22 Aug 2006, 12:47
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

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?

17
18
19
20
21

Last edited by lan583 on 11 Feb 2007, 08:52, edited 1 time in total.
Director
Joined: 06 May 2006
Posts: 791

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22 Aug 2006, 13:08
19 (c)

Since probability is less than 2/5, 12 must be less than 40% of the balls. So there must be at least 60% + 1 yellow balls.
_________________

Uh uh. I know what you're thinking. "Is the answer A, B, C, D or E?" Well to tell you the truth in all this excitement I kinda lost track myself. But you've gotta ask yourself one question: "Do I feel lucky?" Well, do ya, punk?

Senior Manager
Joined: 14 Jul 2005
Posts: 402

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22 Aug 2006, 13:24
agree with paddyboy... 19 it is

Let T be the total number of balls

12/T <2 /5

i.e. T>30

i.e. 12 + y > 30

y>18

Hence C
22 Aug 2006, 13:24
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