AP EAMCET Engineering 26 Apr 2017 Shift 1 Paper

Let E1 be the event that 1W and 3B marbles are transferred, E2 be the event 2W and 2B marbles are transferred, E3 be the event that 3W and 1B marbles are transferred and E4 be the event that 4W and 0B marblesare transferred.
Let A be the event that a black marble is drawn from the bag. Therefore, the required probability is,
=

5 8C4 . 3 4

5 8C4 . 3 4 + 30 8C4 . 2 4 + 30 8C4 . 1 4 +0

=

15

15+60+30

=

1

7