Problem Solving

A bag contains 3 white balls, 3 black balls & 2 red balls. One by one three balls are drawn out without replacement. What is the probability that the third ball is red?

since any ball has equal chances to be white, back or red, then the probability that the third ball is red is 2/8=1/4 (please note that 8 is the sum of all balls , i.e. 3 white balls, 3 black balls & 2 red balls 3+3+2=8)

Dear Anurag

This question is without replacement, your approach would have been right if it were with replacement since it is possible that both the red balls get picked in the first two positions and there is no red ball left for the final position.

Please clarify.

Regards.

mankey wrote:Dear Anurag

This question is without replacement, your approach would have been right if it were with replacement since it is possible that both the red balls get picked in the first two positions and there is no red ball left for the final position.

Please clarify.

Regards.

actually, the answer will be the same with or without replacement

just think - u have some balls in front of u. u are not said the probability of first 2 balls. if u were said, then u would have been right, since first 2 links to the 3d one. but here u have some balls, and nothing is said, so all these balls have the equal right to be the 3d one

moreover, if the q. is what is the probability that the 1st ball is red, u again get the same answer