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A bag contains five white balls and four black balls. Your goal is to draw two black balls.

You draw two balls at random. Once you have drawn two balls, you put back any white balls, and redraw so that you again have two drawn balls. What is the probability that you now have two black balls? (Include the probability that you chose two black balls on the first draw.)

 Apr 23, 2020
 #1
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First way: [5/9 * 4/8  + 4//9 * 3/8] = 4/9

 

2nd way: [9C2 ] = 36 number of ways you can 2 balls

Number of ways of drawing 2 balls of the same color =5C2 + 4C2 =16

Probability =16 / 36 = 4/9

 Apr 23, 2020
 #2
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That's wrong.

Guest Apr 23, 2020

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