Consider a sample of size 3 drawn in the following manner:

Solution

Step 1 of 4

Given that an urn is containing 5 white 7 red balls

The total no.of balls is 5+7=12

Now we have to draw a sample of 3 from the urn

Here given condition is that if we get tire ball we have to returned along with same colour ball

a) We have to find the probability of getting zero white balls

Here getting red ball means all the times we are getting the red ball

First time we are getting the red ball the probability is 7/12

And we returned the ball, with another same colour ball then the no.of balls is 13 and red colour balls are 8 then the probability is 8/13

 Again same like that third time probability is 9/14

Then P(getting 0 white balls )=(7/12)(8/13)(9/14)

                                                =0.2308

Hence the probability of getting zero white balls is 0.2308