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A box contains 7 Yellow balls and 5 blue balls. Select 3

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Senior Manager
Joined: 25 Dec 2003
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A box contains 7 Yellow balls and 5 blue balls. Select 3 [#permalink]

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12 Jul 2004, 07:48
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

A box contains 7 Yellow balls and 5 blue balls. Select 3 balls randomly. What is the probability of choosing 3 blue ones.

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Senior Manager
Joined: 05 Feb 2004
Posts: 290
Location: USA
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12 Jul 2004, 08:45
3 balls can be chosen from 12 in : 12C3 ways
3 blue balls can be chosen from 5 blues in: 5C3 ways

Hence required prob: 5C3/12C3 = 10/220 = 1/22!!
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12 Jul 2004, 08:46
Probability = (Fav. outcome) / (Total Outcome)

Total : selecting 3 balls from 12 balls = 12C3
Favourable : selecting 3 blue from 5 blue balls = 5C3

P = 5C3 / 12C3 (Very lengthy calculation)
Joined: 31 Dec 1969
Location: Russian Federation
Concentration: Entrepreneurship, Technology
GMAT 1: 710 Q49 V0
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GMAT 3: 740 Q40 V50
GMAT 4: 700 Q48 V38
GMAT 5: 710 Q45 V41
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GMAT 7: Q42 V44
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GMAT 9: 740 Q49 V42
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GMAT 12: 670 Q V
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12 Jul 2004, 11:45
I would do:

5/12 x 4/11 x 3/10 = 1/22 and forget about the combinations formula.
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