a box contains 4 bad and 6 good tubes. two are drawn out together. one of them is tested and found to be good. what is the probability that the other one is also good?
6-1=5
4+5=9
5/9
The possibilities (where g = good and b = bad) are:
gg = 6/10*5/9 = 1/3
gb = 6/10*4/9 = 4/15
bg = 4/10*6/9 = 4/15
So, given that one of the pair is g, the probability that you have gg is (1/3) / (1/3 + 4/15 + 4/15) = 5/13 ≈ 0.385
