Posted by jake on Saturday, March 12, 2011 at 11:39am.
If there are 6 blue marbles and 2 red marbles in a bag, what is the probability of picking a blue marble then another blue marble if you do not replace the first marble P(B,B)? 3/4 x 5/7 or is it 3/4 x 6/7?

math  Reiny, Saturday, March 12, 2011 at 11:57am
Prob = (6/8)(5/7) , which was your first choice

math  jake, Saturday, March 12, 2011 at 12:36pm
3/4 x 5/7, but that means you presume you took out a blue marble the first time. How do you know that you didn't take out a red marble, so you still have all six blue marbles when you pick the second time?

math  Reiny, Saturday, March 12, 2011 at 2:26pm
"... but that means you presume you took out a blue marble the first time"
yes, that is the case we wanted, and the 6/8 is the probability that would have happened, and one of the blue marbles has now been picked. 
math  Jose, Wednesday, February 22, 2017 at 10:05pm
The Answer is The Probality of picking a pink Or Blue is 4 divide in 2 is 2 1.2