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## Probability-2

A bag contains 5 blue and 4 black balls. 3 are drawn at random. What is the probability that 2 are blue and 1 is black?

Ans with explantion pls.

Thanks

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Probability of picking Blue in first instance = 5/9
Probability of picking Blue in second instance = 4/8=1/2
Probability of picking Black in three instance = 4/7
Probability of picking (B,B,Black) in 3 random picks = (5/9)*(1/2)*(4/7)
= 10/63
This sequence can be arranged in 3 ways:
(B,B,Black), (B,Black,B), (Black,B,B)

So, Probability = (10/63)*3 = 10/21

Thanks and regards,
Vivek

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Thank you very much.

4. Good post? |
Originally Posted by viveksurya
Probability of picking Blue in first instance = 5/9
Probability of picking Blue in second instance = 4/8=1/2
Probability of picking Black in three instance = 4/7
Probability of picking (B,B,Black) in 3 random picks = (5/9)*(1/2)*(4/7)
= 10/63
This sequence can be arranged in 3 ways:
(B,B,Black), (B,Black,B), (Black,B,B)

So, Probability = (10/63)*3 = 10/21

Thanks and regards,
Vivek
Yeah this may be the answer .

You have considered that the probability without ( Replacement) . But I feel that with replacement the answer may be different.

Although the question doesn't clearly mention with replacement/without replacement , can we assume that the case to be without replacement when no data pertaining to with replacement/without replacement is given.

5. Good post? |
Originally Posted by viveksurya
Probability of picking Blue in first instance = 5/9
Probability of picking Blue in second instance = 4/8=1/2
Probability of picking Black in three instance = 4/7
Probability of picking (B,B,Black) in 3 random picks = (5/9)*(1/2)*(4/7)
= 10/63
This sequence can be arranged in 3 ways:
(B,B,Black), (B,Black,B), (Black,B,B)

So, Probability = (10/63)*3 = 10/21

Thanks and regards,
Vivek
thank you .in the question it doesn't clearly mention that it is with replacement/without replacement , can we assume that this case to be without replacement when no data pertaining to with replacement/without replacement is given.

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