GATE CSE
First time here? Checkout the FAQ!
x
0 votes
88 views
There are 2 white and 4 black balls in urn A; in urn B, there are 4 white and 7 black balls. If one ball is randomly replaced from A into B and a ball is drawn from B then find the probability for the ball to be a white one?
asked in Probability by Active (1.3k points)   | 88 views
13/36=0.36?
is it 17/36?
$\frac{2}{6}\times \frac{5}{12}+\frac{4}{6}\times \frac{4}{12}=\frac{13}{36}$

1 Answer

+2 votes
Best answer

There are possible scenarios :

A) White ball is replaced from A into B  and  white ball is picked up :   (1 / 3) * (5 / 12)  =  5 / 36

B) White ball is replaced from A into B  and  black ball is picked up :   (1 / 3) * (7 / 12)  =  7 / 36

C) Black ball is replaced from A into B and white ball is picked up :      (2 / 3) * (4 / 12)  =  8 / 36

D) Black ball is replaced from A into B and black ball is picked up :      (2 / 3) * (8 / 12)  =  16 / 36

So P(ball picked will be white one) :        = [ A) + C) ] / [ A) + B) + C) + D) ]

                                                                = (5 + 8) / (5 + 7 + 8 + 16)

                                                                = 13 / 36

Hence the correct answer is 13 / 36

 

answered by Veteran (66.2k points)  
selected by


Top Users May 2017
  1. Prashant.

    130 Points

  2. akankshadewangan24

    102 Points

  3. Tesla!

    90 Points

  4. Vishal Goel

    20 Points

  5. sh!va

    20 Points

  6. Arjun

    14 Points

  7. Krunal2016

    12 Points

  8. Raushank2

    10 Points

  9. Habibkhan

    10 Points

  10. akash.dinkar12

    10 Points

Monthly Topper: Rs. 500 gift card
Top Users 2017 May 01 - 07
  1. Prashant.

    130 Points

  2. akankshadewangan24

    102 Points

  3. Tesla!

    90 Points

  4. Vishal Goel

    20 Points

  5. sh!va

    20 Points


22,195 questions
28,249 answers
63,693 comments
24,385 users