Find the chance of drawing 2 white balls in succession from a bag containing 5 red and 7 white balls, the ball first drawn not being replaced.

Bag contains 5 red balls and 7 white balls. So the total number of all favorable cases is n(S) = 5+7=12


Let A represents first ball as white ball, and B be second ball as white ball.


Then the probability of drawing two white balls without replacement is


P(2 white balls without replacement)



(as there are 7 white balls in first draw out of 12 balls, and 6 white balls in second draw out of 11 balls as the balls are not replaced)


Hence the required probability is


3