Question

Bag contains 10 white and 3 black balls. balls are drawn one by one without replacement till all the black balls are drawn. find the probability that all black balls are drawn by the 6th draw.

Answer 1

 

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Probability question of drawing balls from a bag.

A bag contains 10 white and 3 black balls.Balls are drawn one by one without replacement till all the black balls are drawn.Find the probability that all black ballls are drawn by the 6th draw

  

 

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asked Jun 24, 2016 by suman1176



1 Answer

Total no: of balls = 13

probablity of drawing a white ball in 1st draw is 10/13

white ball in the 2nd draw is 9/12

white ball in the 3rd draw is 8/11

a black ball in 4th draw is 3/10

a black ball in the 5th draw is 2/9

a black ball in the 6th draw is 1/8

Therefore the required probablity is 10/13 x 9/12 x 8/11 x 3/10 x 2/9 x 1/8 = 4320/1235520 = 432/123552

Answer 2

Answer:

Step-by-step explanation:

The required event is we drawn 2 black balls and 3 white balls in the first 5 draws and  the last third black ball is drawn in the 6th draw.  

Probability that we get a black ball in the 6th draw is 1/8,

because there are only 8 balls and only one black ball is drawn in the 6th draw.

Probability of drawing 2 black balls and 3 white balls in the first 5 draws = 3C2.10C3/13C5

Therefore the required probability = (3C2.10C3/13C5)(1/8) = 0.0350