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 07-05-2012, 01:37 AM #1 stranger   Join Date: Jul 2012 Posts: 2 three balls Hi I should be very grateful if someone a lot cleverer than me could kindly look at this and give me an answer. bag with one white, red, black ball. random picks. how often black ball chosen 4; 5; 6 times in a row. Many thanks in anticipation of your help with this. Dave
 07-05-2012, 02:29 AM #2 enthusiast   Join Date: Feb 2011 Location: Kew Gardens Posts: 52 Re: three balls The odds of choosing any particular ball are 1/3 on a single pick. So the odds of choosing the black ball n times in a row in n picks are just (1/3)^n.
07-05-2012, 03:11 AM   #3
old hand

Join Date: May 2012
Posts: 1,906
Re: three balls

Quote:
 Originally Posted by Bohr8346 The odds of choosing any particular ball are 1/3 on a single pick. So the odds of choosing the black ball n times in a row in n picks are just (1/3)^n.
Unless, the chosen ball is not returned to the bag. In such a case, the odds are approximately 0.000000000000.

 07-05-2012, 03:30 AM #4 grinder     Join Date: Sep 2011 Location: an octopus's garden Posts: 603 Re: three balls The title of your post made me click for an entirely different reason than you intended (prolly).
07-05-2012, 04:37 AM   #5

Join Date: Jul 2011
Location: Laaaaandaaaan
Posts: 875
Re: three balls

Quote:
 Originally Posted by AnonyMouse1 The title of your post made me click for an entirely different reason than you intended (prolly).
I was hoping for an epic images thread

 07-05-2012, 08:21 AM #6 grinder     Join Date: Jan 2009 Location: Sydney, Aus Posts: 24,895 Posts: 690 Re: three balls Are there cases of people having three testicles? Edit: I see polyorchidism is very rare but is a known congenital disorder.
 07-05-2012, 08:39 AM #7 old hand     Join Date: Jul 2010 Posts: 1,835 Re: three balls Epic 1st post. I guess it shows that I have maturity issues when I can't resist clicking on a "3 balls" thread thinking I'm going to get something other than a question about calculating probability.
07-05-2012, 09:12 AM   #8
Carpal \'Tunnel

Join Date: Jul 2005
Location: (X'X)^(-1)X'Y
Posts: 9,530
Re: three balls

Quote:
 Originally Posted by Qwazi Are there cases of people having three testicles? Edit: I see polyorchidism is very rare but is a known congenital disorder.
i think the lead singer of crash test dummies has this

 07-05-2012, 12:29 PM #9 stranger   Join Date: Jul 2012 Posts: 2 Re: three balls thanks Bohr 8346 I don't know what that means? Dave
07-05-2012, 02:36 PM   #10
Pooh-Bah

Join Date: Jul 2009
Location: facepalming my way into history
Posts: 5,928
Re: three balls

Quote:
 Originally Posted by striker44 thanks Bohr 8346 I don't know what that means? Dave
This only applies if the ball is put back in ( duh! ) and you only want the chance of getting a black ball in straight picks ( i.e. not 3 blacks in 5 picks etc, but only black black black in 3 picks ).

The chance of getting a black ball ( like any other ball ) is 1/3. To get the final chance you multiply that chance per itself as many times as you want black balls in a row.

Example: 4 black balls in a row -> 1/3 x 1/3 x 1/3 x 1/3
Example: 6 black balls in a row -> 1/3 x 1/3 x 1/3 x 1/3 x 1/3 x 1/3

If you want to get the chance of 4 black balls in 6 tries, including the various combinations, the equation get's more complicated.

If you still don't understand how it works, you might want to try in your native language somewhere.

Last edited by YouR_DooM; 07-05-2012 at 02:43 PM.

 07-05-2012, 07:49 PM #11 old hand     Join Date: Jul 2010 Posts: 1,835 Re: three balls Step 1: Figure out your chances that you pick it one time if there are three balls. It's one in three, 1/3, or 33%. (If you had 4 balls it would be 1/4, 5 balls 1/5, and so on.) Step 2: To figure the odds of picking that ball a certain number of times in a row you just multiply the number of picking it once by itself. (So for twice its 1/3 x 1/3, for 10 times you do 1/3 x 1/3 x 1/3.... 10 times. Challenge Question If you have 4 balls and non of them are alike, what are the odds you pick the same ball 100 times in a row? Use only a basic calculator without the ^ that you didn't understand. Show all your work and give your answer in your next post and show all your work. If you do that I bet you end up deciding that there MUST be an easier way and it will lead you to figure out what the ^ is for by the end of it all :-)

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