Posted by **Gina** on Tuesday, October 2, 2012 at 5:25pm.

An urn contains 5 red balls and 10 white balls. 6 balls are randomly drawn and not replaced. What is the probability that 3 or fewer balls drawn are red?

- Statistics - math -
**Reiny**, Tuesday, October 2, 2012 at 5:40pm
could be 3 red, 3 white

could be 2 red, 4 white

could be 1 red, 5 white

could be all white

prob of those taken in order from top to bottom

= C(6,3) (5/15)(4/14)(3/13)(10/12)(9/11)(8/10)

+ C(6,2) (5/15)(4/14)(10/13)(9/12)(8/11)(7/10)

+ C(6,1) (5/15)(10/14)(9/13)(8/12)(7/11)(6/10)

+ C(6,0) (10/15)(9/14)(8/13)(7/12)(6/11)(5/10)

= .... you do the button pushing

Can you see the pattern ?

- Statistics - math -
**Gina**, Tuesday, October 2, 2012 at 6:25pm
The answer is supposed to be 0.04 + 0.25 + 0.42 + 0.24 = 0.95

However, when I do the math above, I get 0.01 + 0.03 + 0.04 + 0.04 = 0.12.

Where am I making the error in calculating this?

## Answer This Question

## Related Questions

- statistics - An urn contains white and red balls. Four balls are randomly drawn ...
- statistics - An urn contains white and red balls. Four balls are randomly drawn ...
- Pre Algebra Probability - Each of two urns contains green balls and red balls. ...
- MATH(STATISTICS) - Urn A contains R red balls and W white balls, urn B contains ...
- statistics - An urn contains 10 balls of which 6 are white, 3 are red and 1 is ...
- statistics - An urn contains 10 balls of which 6 are white, 3 are red and 1 is ...
- Math help? - I am kind of stuck on this one Each of two urns contains green ...
- Finite Math-Probability - Suppose we have an urn with 10 white balls and 6 red ...
- Another math related question - Two urns both contain green balls and red balls...
- math - A box contains 6 red balls, 4 white balls, and 5 green balls. If three ...

More Related Questions