Posted by **Stuck** on Monday, May 3, 2010 at 8:45pm.

"In vase A, there are 3 red balls and 5 white balls. In vase B, there are 6 red balls and 4 white balls. Two balls are to be drawn at random, without replacement, from each vase. What is the probability of selecting 4 red balls?"

(Answer: 1/28)

So I thought about doing 4 cases and then adding them up (don't pick red ball in A, don't pick red ball in B...pick red ball in A, pick red ball in B...etc...).

I did this:

(3/8)(3/7)(6/10)(6/9) +

(3/8)(2/7)(6/10)(5/9) +

.....

But it doesn't work. What am I doing wrong?

- Math -
**Reiny**, Monday, May 3, 2010 at 9:46pm
Since you pick 2 from each vase, and you want 4 reds, there is only one way, that is, you pick 2 from A and 2 from B.

which is C(3,2)/(C(8,2) * C(6,2)/C(10,2)

= 3/28 * 15/45 = 1/28

- Math -
**Stuck**, Monday, May 3, 2010 at 10:17pm
Oh yeah! Thank you!

## Answer This Question

## Related Questions

- statistics - A jar contains 7 red balls, 5 green balls, 4 blue balls, and 3 ...
- Math - A bag contains three black balls, four white balls and five red balls. ...
- physics - in a bag there are 20 red 30black 40 blue50 white balls. what is the ...
- Statistic - A urn contains 21 red balls, 14 white balls If we randomly select 2 ...
- Finite Math-Probability - Suppose we have an urn with 10 white balls and 6 red ...
- math - A box contains 6 red balls, 4 white balls, and 5 green balls. If three ...
- Strayer University - An urn contains white balls and red balls. If Juan chooses ...
- statistics /pure maths - A box contains N identical balls of which 4 are Red, 3 ...
- math - A basket contains 15 red numbered balls and 10 white numbered balls. A ...
- College Discrete - An urn contains n > 0 white balls and m > 0 black ...

More Related Questions