The urn contains 5 white and 4 black balls, differing only in color. Get out two balls at random.

The urn contains 5 white and 4 black balls, differing only in color. Get out two balls at random. Find the probability that the balls are of different colors.

A big event consists of two small independent ones, here is its formula:
P (C) = P (A) * P (B)

Big event – 1 white ball and 1 black ball
Substitute in the formula and get:
P (C) = 1 b. and 1 tsp.
And- multiplication
We get:
P (C) = P (b) * (Rh)

To find a small event:
P (A) = favorable outcomes (m) / number of total outcomes (n)

There are 9 outcomes in total, because 5 white and 4 black
P (1) = 5/9 = 0.555. (5 because 5 white balls, these are favorable for us)
P (2) = 4/9 = 0.444 similarly

Now we substitute in our formula:
P (C) = 0.555 * 0.444 = 0.246