A box has

    \[5\]

blue and

    \[4\]

red balls. One ball is drawn at random and not replaced. Its colour is also not noted. Then another ball is drawn at random. What is the probability of second ball being blue?
A box has

    \[5\]

blue and

    \[4\]

red balls. One ball is drawn at random and not replaced. Its colour is also not noted. Then another ball is drawn at random. What is the probability of second ball being blue?

Given that the box has

    \[5\]

blue and

    \[4\]

red balls.

Let us consider

    \[{{E}_{1}}\]

be the event that first ball drawn is blue and

    \[{{E}_{2}}\]

 be the event that first ball drawn is red.

And, E is the event that second ball drawn is blue.

Now, the probability of E is:

Therefore, the required probability is

    \[5/9\]

.