PROBABILITY QUESTION

Question

Comments

I am getting 0.78.

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What's your appraoch?

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I have added it as an answer, please check it.

Answer 1

Please correct me if I'm wrong.

Comments

Great answer,, seems correct

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why ordering is considered in these question

eg: (1) first black ,second red

and

(2) first red , second black  

and

(3)both  are black

why are we are considering 1 and 2 case separately??

Answer 2

1. Probability that at least at least one black ball is picked in the first two pickings = $1- (75/100 \times 75/100) = 0.44 $

2. Probability that at least one black ball with a red dot is picked in the first two pickings = $ 1- (95/100 \times 95/100) = 0.09 $

The probability that no black ball with a red dot is picked given that at least one black ball is picked is $(1 -2)/1 = 0.35/ 0.44 = 0.79 $