There are 4 white, 4 yellow, 1 blue balls in the urn. At random, 4 balls were removed from the basket without returning.

There are 4 white, 4 yellow, 1 blue balls in the urn. At random, 4 balls were removed from the basket without returning. Find the probability that among them there are 2 white, 2 yellow.

The urn contains 4 + 4 + 1 = 9 balls.
The number of ways to extract 4 balls out of 9:
C (9.4) = 9! / (4! (9 – 4)!) = 6 7 8 9 / (1 2 3 4) = 126.
The number of ways to extract 2 white balls out of 4:
C (4,2) = 4! / (2! (4 – 2)!) = 3 4 / (1 2) = 6.
Number of ways to draw 2 yellow balls out of 4:
C (4,2) = 4! / (2! (4 – 2)!) = 3 4 / (1 2) = 6.
The probability that 2 white and 2 yellow balls will be drawn:
P = C (4.2) C (4.2) / C (9.4) = 6 6/126 = 2/7 = 0.2857.
Answer: The probability of drawing 2 white and 2 yellow balls is 0.2857.