Tuesday

September 23, 2014

September 23, 2014

Posted by **Katia** on Monday, December 13, 2010 at 8:17pm.

From the box containing 5 red balls, 7 blue balls, 10 black balls. you select 4 balls

what is the probabilty that EXACTLY 2 balls are black.

i know that you start it/set it up like this:

c(10,2)c(2,1) divided by c(22,4)

and i can get the answer by plugging it in the calculator. but i would like to know how to solve it by hand. help?

- Math -
**Reiny**, Monday, December 13, 2010 at 10:02pmI answered it for you here

http://www.jiskha.com/display.cgi?id=1292286864

to evaluate without a calculator ? Wow

C(10,2) = 10!/(8!2!) = 10*9/2 = 45

C(12,2) = 12!/(10!2!) = 12*11/2 = 66

C(22,4) = 22!/(18!4!) = 22*21*20*19/(4*3*2*1) = 7315

You sure you want to do this "by hand" ?

**Answer this Question**

**Related Questions**

Math - my problem is: From the box containing 5 red balls, 7 blue balls, 10 ...

Math - A box containing 20 yellow balls, 9 red balls and 6 blue balls. If the ...

maths-probabilty - A box contains 5 red balls and 6 black balls. in how many ...

maths-probabilty(urgently needed) - A box contains 5 red balls and 6 black balls...

Math - Four balls are simultaneously picked at random from a jar containing 2 ...

math - A box contains 8 blue balls and 2 red balls. Three balls are selected ...

math - we have box,in box 3 white balls,4 red balls,4 black balls..how i choose ...

Statistics - I have two boxes with balls; box #1 and box #2. Box #1 has 3 red ...

Probability again - A box contains 6 red balls, 4 blue balls, and 2 green balls...

Basic Mathematics - A bag contains 2 red balls, 3 blue balls and 5 green balls. ...