What is the answer of this problem?

[Guest]

Consider a basket containing 4 red balls, 2 white balls and one green, blue and black. How many selection are possible under the given condition 2 alike, 2 alike and 2 different ?

[Math Tutor]

The second sentence is unclear and I do not get it.

[Guest]

First condition is 2 similar color balls.
Second condition is 2 similar color balls + 2 different color balls, total 4 balls at a time.

[Guest]

2 balls with the same color is
[tex]{{9}\choose{4}} + {{9}\choose{2}}[/tex]

[Guest]

I think that the answer above is wrong.

All combinations of selecting 2 balls are: [tex]{9}\choose{2}[/tex]
2 same color balls can be selected by [tex]{{4}\choose{2}} \times {{2}\choose{2}} = {{4}\choose{2}}[/tex]
The answer is: [tex]\frac{{4}\choose{2}}{{9}\choose{2}}[/tex]

[leesajohnson]

Selection for two same color ball is 9/2

=> 9/4 + 9/2

=> Answer is (4/2) / (9/2).