statistics
posted by Moses joseph .
From a bag containing 6 black and 4 white balls, 2 balls are selected,one after the other,without replacement. Find (a) the probability that they are both black (b)the probability that they are both the same colour, (c) probability that they are different colours.

total balls = 10
without replacement, so you'll have one less ball each time you draw
I'll do the first one for you. You can figure out how to the rest.
P(both black) = (6/10)(5/9)
Explanation: During the first draw, there are 6 black balls and a total of 10 balls. During the second draw (because there was no replacement), there are now 5 black balls and a total of 9 balls.